Beat flour, eggs, and salt together in a large bowl until smooth. Gradually stir in milk and 1 ½ tablespoons melted butter. Cover batter with plastic wrap; rest in the refrigerator at least 2 hours.

Combine cottage cheese, cream cheese, sugar, and vanilla extract in a blender; blend until filling is smooth.

Melt a bit of butter in a large skillet or crêpe pan over medium heat. Spoon a small amount of batter into the skillet; immediately swirl the skillet to spread batter in a thin layer. Cook until set, about 30 seconds. Flip; cook until second side is cooked, about 10 seconds more. Transfer to a plate; cool. Repeat with remaining butter and batter.