Use a round cookie cutter (also called a “ring cutter”) to cut out rounds of dough. I usually cut out 3” diameter circles.
Into the center of each shell, put about 1/4 cup filling. (For the breakfast empanadas, smear on a tablespoon of cheese and put in an equal blob of jelly.) Then, fold the circle in half, using a little water on the still-exposed dough edge and press tightly to seal.
Use the tines of a fork to go around the edge and make sure the dough is completely sealed. Repeat until you run out of dough or filling.