Preheat the oven to 375°F. Line a 12-cup muffin tin with paper liners or grease lightly.
In a blender, combine the cottage cheese, eggs, milk, oil, vanilla, and sugar. Blend until smooth.
In a large bowl, whisk together the flour, baking powder, baking soda, and salt.
Pour the blended cottage cheese mixture into the dry ingredients. Stir gently until almost combined.
Toss the blueberries with 1 tablespoon of flour, then fold them gently into the batter.
Divide the batter between the muffin cups, filling each about three-quarters full. Sprinkle with coarse sugar if desired.
Bake for 20 to 24 minutes, or until the tops are lightly golden and a toothpick inserted in the centre comes out clean or with a few moist crumbs.
Let the muffins cool in the pan for 5 minutes, then transfer to a rack. Serve warm or at room temperature.