Prepare crepe batter: In a medium bowl, whisk together eggs and milk. When well combined, whisk in flour until smooth. Set aside to rest for at least one hour.
Heat a 6-inch, nonstick skillet over medium-high heat. Lightly spray pan and return to heat. Pour a scant 1/4 cup of batter into the pan, swirling to cover the bottom evenly. Cook for about 30 seconds or until it is just set and the bottom is lightly browned. Turn the crepe over carefully with spatula. Cook for an additional 15 seconds or until set. Remove from pan and place on a piece of waxed paper. Continue cooking and stacking, placing a square of waxed paper in between each crepe, until all batter has been cooked. You may end up with 14 crepes, two are allowed for breakage.
Prepare filling: Using a wooden spoon, combine ricotta, egg yolks, diced mozzarella, Pecorino Romano cheese, salt and pepper until well-blended.
Lay crepes out in a single layer. Place a heaping tablespoonful of the ricotta mixture in the center at the top of the crepe, spreading out to the edges. Fold the ricotta-covered portion over onto the crepe. Fold the edges in and roll into a firm packet.
Spread marinara sauce over the bottom of a 13 x 9 x 2-inch baking pan. Lay rolled crepes on top of the sauce. Put a slice of mozzarella on top of each rolled crepe. Bake in a preheated 375 degree F oven until filling is hot and cheese has melted, about 20 minutes. Serve, allowing 2 pieces per person.Makes 6 Source: