Blintzes are crepes filled with cheese and topped with sour cream and jam. Prepare the crepes by mixing milk, eggs, salt, and flour in a bowl until smooth. Heat a small skillet or crepe pan until water sprinkled into the pan sizzles. Pour in the crepe mix and thinly cover the bottom of the pan, tipping it from side to side and pouring off any excess that doesnt immediately stick. Cook the crepes on one side only, just until they look dry (about one minute). Remove. To prepare the filling, mix cottage cheese, egg, vanilla, and sugar in a bowl until smooth. Spread two tablespoons of filling onto the corner of each crepe. Fold the sides of the crepe over to make an envelope (top, left, right, then bottom) until youve made a square pouch around the filling. Melt butter in a large skillet. Place the filled crepes seam-side down and cook until golden brown.