Ligia Rossi, who grew up in Costa Rica, is a fan of alfajores, soft, melt-in-your-mouth sandwich cookies filled with dense, creamy, caramel-flavored dulce de leche. These alfajores are tender thanks to the egg yolks, butter and cornstarch. Make an easy dulce de leche filling and place it between two cookies. The cookies are ready when they are still pale but set and the bottom is lightly golden. Baking time is key for a delicate cookie.
Note: Rossi makes a triple batch of these cookies; To expand, multiply the measurements by three and instead of 2 egg yolks, use 1 whole egg plus 4 yolks. Make as many cans of dulce de leche as you want. You can store an unopened can of dulce de leche (it should be free of dents or lumps) for several months. Or use it for ice cream, brownies, pancakes, churros, or eat it alone with a spoon.
