Heat a large skillet over medium-high heat. Add the ground beef, ground lamb, chopped onion, pine nuts, ground cinnamon, salt, and black pepper. Cook and stir until the meat is crumbly, evenly browned, and no longer pink. Drain any excess grease.

Stir in the lemon juice and taste the mixture. Adjust the seasonings if needed. Allow the meat mixture to cool.

Preheat the oven to 350 degrees F (175 degrees C). Lightly grease a baking sheet or line it with parchment paper.

Roll out the thawed puff pastry sheets on a floured surface to about 1/8 inch thick. Use a sharp 3-inch round cookie cutter to cut out at least 9 rounds per sheet.

Brush the inside edges of each pastry round with a little water. Place about 2 teaspoons of the cooled meat filling into the center of each round. Fold the pastry round in half to cover the filling and seal the edges well. Repeat with the remaining dough circles and filling.

Place the filled pies onto the prepared baking sheet. Brush the tops of the pies with the beaten egg.

Bake in the preheated oven until the pies are golden brown, which usually takes about 15 to 20 minutes.

Once baked, remove the pies from the oven and let them cool slightly before serving. Enjoy your delicious meat pies!