In a mixing bowl, whisk together flour, eggs, milk, sugar, and melted butter until smooth.

Heat a frying pan over medium heat and pour in a small amount of batter, swirling to coat the bottom. Cook until edges are golden, then flip and cook for another minute.

In a bowl, mix together ricotta cheese, cream cheese, sugar, and vanilla extract until well combined.

Place a spoonful of cheese filling in the center of each crepe, fold the sides over, and roll up tightly.

In the same frying pan, cook the filled blintzes until golden brown on both sides.