Cauliflower & Potato Gratin with Silky Béchamel (Restaurant “Cold Roux” Option)
This cozy cauliflower and potato gratin with silky béchamel is the ultimate make-ahead side for Canadian and U.S. home cooks who want French comfort with weeknight simplicity. It’s based on my YouTube video, with a few small tweaks I made after publishing for better texture: the potatoes are par-cooked just to al dente, the béchamel is dialed to a perfectly spoonable consistency, and you get two béchamel options — the restaurant-style oil-and-flour “cold roux” whisked into hot milk for a super-smooth, lump-free sauce, or a classic butter roux. It’s the kind of pan that sits next to roast chicken, steak, or fish and steals the show.
Why you’ll love it
- Two béchamel methods: choose the cold roux (oil + flour) like in pro kitchens or the classic butter roux.
- Creamy but light: sauce coats the veg without turning gluey.
- Flexible: make in one dish or portion into individual ramekins.
- Pairs with everything: from a steak au poivre vibe to chicken and salads.
A few related favorites for inspiration: Parisian potatoes (butter-basted “Pommes Parisiennes”), traditional gratin dauphinois, creamy zucchini gratin, authentic Greek moussaka, pastitsio with thick béchamel, and a simple homemade tomato sauce if you like a red-sauce contrast on the table.
Ingredients (Imperial + Metric; weights first)
Vegetables
- 800 g (1¾ lb) potatoes (waxy/yellow like Yukon Gold, sliced ½ in / 1–1.2 cm)
- 1,000 g (2.2 lb) cauliflower, cut in bite-size florets
For cooking water
- 20–30 g (1–2 tbsp) fine sea salt in 2–3 L (2–3 qt) water
Béchamel — choose one (both yield ~1 L sauce)
A) Restaurant “Cold Roux” (Oil + Flour added cold to hot milk) — super silky
- 1,000 ml (4 cups) whole milk
- 70–80 g (½–⅔ cup) all-purpose flour (see note)
- 70–80 ml (5–6 tbsp) neutral oil (canola/sunflower)
- 15 g (2½ tsp) fine sea salt, 2 g (½ tsp) black pepper, pinch nutmeg
- (Optional color): 1 g turmeric
B) Classic Butter Roux (traditional French béchamel)
- 1,000 ml (4 cups) whole milk
- 70–80 g (5–6 tbsp) unsalted butter
- 70–80 g (½–⅔ cup) all-purpose flour
- 15 g (2½ tsp) fine sea salt, 2 g (½ tsp) black pepper, pinch nutmeg
To finish
- 150–200 g (1½–2 cups) Emmental or Gruyère, shredded
- (Optional inside layer) extra 50–80 g (½–¾ cup) cheese
Note on ratios (optimized): In the video, I demo a generous oil-flour paste. For perfect oven-set yet creamy results, aim for ~70–80 g flour and the same weight in fat per 1 L milk. Add gradually to reach “coats-a-spoon” thickness.
Step-by-step
- Prep & blanch the vegetables
- Bring a large pot of well-salted water to a boil (about 1% salinity).
- Add potato slices; simmer 5–6 minutes until just al dente (they’ll finish in the oven). Lift out and drain.
- In the same pot or a fresh one, simmer cauliflower florets 6–8 minutes until tender but not mushy; drain well.
- Bring a large pot of well-salted water to a boil (about 1% salinity).
- Make the béchamel (choose one)
- A) Cold Roux (Oil + Flour into hot milk):
Warm milk with salt, pepper, nutmeg (and optional turmeric). In a bowl, whisk flour + oil to a smooth paste. Off heat, whisk a few spoonfuls of paste into the hot milk, return to medium heat, and whisk as it thickens gently. Add paste gradually until the sauce lightly coats the back of a spoon. Simmer 2–3 minutes to cook the flour. - B) Classic Butter Roux:
Melt butter, whisk in flour, cook 1–2 minutes (no color). Off heat, whisk in warm milk in splashes, return to medium heat, and cook until silky and nappant (2–4 minutes). Season with salt, pepper, nutmeg.
- A) Cold Roux (Oil + Flour into hot milk):
- (Optional) Whisk in a small handful of cheese for extra gloss.
- Assemble
- Butter or oil a 9×13-in (≈23×33 cm) baking dish.
- Layer potatoes, then cauliflower. Ladle béchamel to coat generously (don’t drown). Sprinkle some cheese inside for creaminess. Repeat layers if needed. Finish with a thick, even blanket of cheese.
- Butter or oil a 9×13-in (≈23×33 cm) baking dish.
- Bake & gratinate
- Bake 15–20 minutes at 375–400°F (190–200°C) until bubbling at the edges.
- Switch to broil 2–4 minutes for a deep golden crust. Rest 5–10 minutes so it slices cleanly.
- Bake 15–20 minutes at 375–400°F (190–200°C) until bubbling at the edges.
Tips for success
- Texture control: Keep the potatoes slightly firm after blanching; they’ll finish in the oven.
- Silk, not glue: Add the cold roux in stages; stop when nappant. If too thick, whisk in a splash of milk.
- Cheese balance: A bit inside the gratin improves mouthfeel; the rest on top for browning.
- Make-ahead: Assemble, chill, and bake before serving. Add 5–10 minutes to the bake time from cold.
- Pair with steak au poivre or a lighter plate like homemade Caesar salad.
Substitutions
- Potatoes: Yukon Gold → russet (slightly fluffier) or red potatoes (hold shape).
- Cheese: Emmental/Gruyère → creamy Roquefort sauce side vibe, or mild cheddar.
- Milk: whole → 2% (slightly lighter) or lactose-free.
- Gluten-free: swap flour for a GF all-purpose blend.
- Add-ins: sautéed leeks or caramelized onions; blanched broccoli for a mixed-veg gratin.
FAQ
Is the oil-and-flour method really better?
It’s extremely smooth and very forgiving. Because the paste goes cold into hot milk, lumps are unlikely and the texture stays glossy.
Can I skip the bake and only broil?
You can (as in the video), but a short bake sets the béchamel so portions slice neatly and don’t ooze.
How do I avoid watery gratin?
Drain veg very well; let steam off for a minute. Don’t overshoot sauce thickness; nappant is the target.
Can I freeze it?
Yes, though cauliflower softens after thawing. Reheat, then broil to refresh the crust.
Suggested posts (serve with or similar)
- Traditional gratin dauphinois
- Parisian potatoes
- Creamy mushroom sauce for steak
- Homemade garlic butter
- Homemade ranch dressing
- Creamy tomato pasta
- Homemade bolognese
- Homemade brioche
- Crispy beer-battered fish & chips
- Creamy Tuscan chicken
Cauliflower & Potato Gratin with Silky Béchamel (Restaurant “Cold Roux” Option)
Ingredients
Vegetables
- 800 g 1¾ lb potatoes (waxy/yellow like Yukon Gold, sliced ½ in / 1–1.2 cm)
- 1,000 g 2.2 lb cauliflower, cut in bite-size florets
For cooking water
- 20 –30 g 1–2 tbsp fine sea salt in 2–3 L (2–3 qt) water
Béchamel — choose one (both yield ~1 L sauce)
A) Restaurant “Cold Roux” (Oil + Flour added cold to hot milk) — super silky
- 1,000 ml 4 cups whole milk
- 70 –80 g ½–⅔ cup all-purpose flour (see note)
- 70 –80 ml 5–6 tbsp neutral oil (canola/sunflower)
- 15 g 2½ tsp fine sea salt, 2 g (½ tsp) black pepper, pinch nutmeg
- Optional color: 1 g turmeric
B) Classic Butter Roux (traditional French béchamel)
- 1,000 ml 4 cups whole milk
- 70 –80 g 5–6 tbsp unsalted butter
- 70 –80 g ½–⅔ cup all-purpose flour
- 15 g 2½ tsp fine sea salt, 2 g (½ tsp) black pepper, pinch nutmeg
To finish
- 150 –200 g 1½–2 cups Emmental or Gruyère, shredded
- Optional inside layer extra 50–80 g (½–¾ cup) cheese
Instructions
Prep & blanch the vegetables
- Bring a large pot of well-salted water to a boil (about 1% salinity).
- Add potato slices; simmer 5–6 minutes until just al dente (they’ll finish in the oven). Lift out and drain.
- In the same pot or a fresh one, simmer cauliflower florets 6–8 minutes until tender but not mushy; drain well.
Make the béchamel (choose one)
A) Cold Roux (Oil + Flour into hot milk):
- Warm milk with salt, pepper, nutmeg (and optional turmeric). In a bowl, whisk flour + oil to a smooth paste. Off heat, whisk a few spoonfuls of paste into the hot milk, return to medium heat, and whisk as it thickens gently. Add paste gradually until the sauce lightly coats the back of a spoon. Simmer 2–3 minutes to cook the flour.
B) Classic Butter Roux:
- Melt butter, whisk in flour, cook 1–2 minutes (no color). Off heat, whisk in warm milk in splashes, return to medium heat, and cook until silky and nappant (2–4 minutes). Season with salt, pepper, nutmeg.
- (Optional) Whisk in a small handful of cheese for extra gloss.
Assemble
- Butter or oil a 9×13-in (≈23×33 cm) baking dish.
- Layer potatoes, then cauliflower. Ladle béchamel to coat generously (don’t drown). Sprinkle some cheese inside for creaminess. Repeat layers if needed. Finish with a thick, even blanket of cheese.
Bake & gratinate
- Bake 15–20 minutes at 375–400°F (190–200°C) until bubbling at the edges.
- Switch to broil 2–4 minutes for a deep golden crust. Rest 5–10 minutes so it slices cleanly.
Video
Notes
Tips for success
- Texture control: Keep the potatoes slightly firm after blanching; they’ll finish in the oven.
- Silk, not glue: Add the cold roux in stages; stop when nappant. If too thick, whisk in a splash of milk.
- Cheese balance: A bit inside the gratin improves mouthfeel; the rest on top for browning.
- Make-ahead: Assemble, chill, and bake before serving. Add 5–10 minutes to the bake time from cold.
- Pair with steak au poivre or a lighter plate like homemade Caesar salad.
Substitutions
- Potatoes: Yukon Gold → russet (slightly fluffier) or red potatoes (hold shape).
- Cheese: Emmental/Gruyère → creamy Roquefort sauce side vibe, or mild cheddar.
- Milk: whole → 2% (slightly lighter) or lactose-free.
- Gluten-free: swap flour for a GF all-purpose blend.
- Add-ins: sautéed leeks or caramelized onions; blanched broccoli for a mixed-veg gratin.
FAQ
Is the oil-and-flour method really better?It’s extremely smooth and very forgiving. Because the paste goes cold into hot milk, lumps are unlikely and the texture stays glossy. Can I skip the bake and only broil?
You can (as in the video), but a short bake sets the béchamel so portions slice neatly and don’t ooze. How do I avoid watery gratin?
Drain veg very well; let steam off for a minute. Don’t overshoot sauce thickness; nappant is the target. Can I freeze it?
Yes, though cauliflower softens after thawing. Reheat, then broil to refresh the crust.
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