1. Prepare the filling. Heat a dry skillet over medium heat (I don’t add oil, because ground beef usually has enough fat). Add ground beef, break it up with a spatula. Add finely chopped onion. Cook until the beef is cooked through (about 6-8 minutes).
2. Place mozzarella in a large bowl and melt in a microwave (you can also use a double boiler on the stove). Add egg (beaten with a fork), almond flour, baking powder and salt. Mix with your hands until uniform dough forms (it should be done while mozzarella is still warm).
3. Divide the dough into 15 pieces. On a lightly floured surface (use almond flour), roll each piece in a circle. Place some filling to one side of each circle. Fold each turnover in half, enclosing the filling, and press the edges together with your fingers.
4. Preheat oven to 350F (180C). Place sealed turnovers on a baking sheet lined with a silicone mat or parchment paper. Brush with egg wash (egg mixed with a little bit of water). Bake turnovers in the preheated oven for 10-15 minute, until light brown. Sprinkle with Parmesan cheese, let cool a little and enjoy!