In a medium saucepan, heat 1 cup (240 ml) of water and the butter over medium heat until the butter melts.
In a large bowl, whisk together the flour, 2 teaspoons (12 g) of salt, and 1/4 teaspoon of paprika. Pour the warm butter mixture into the flour. Mix with your hands until a smooth dough forms. Wrap the dough in plastic wrap and chill in the refrigerator for at least 2 hours.
Heat 2 tablespoons (30 ml) of olive oil in a large skillet over medium heat. Add the ground beef and cook until browned, about 10 minutes. Ensure the meat reaches a safe internal temperature of 160°F (71°C) as measured by a food thermometer.
Remove the beef with a slotted spoon and set it aside. Leave about 2 tablespoons (30 ml) of drippings in the pan. Add the remaining 1 tablespoon (15 ml) of olive oil to the skillet.
Add the minced onion and cook for 10 minutes until soft. Stir in the bell peppers, peas, garlic, oregano, 1 teaspoon (6 g) of salt, 1/2 teaspoon of paprika, red pepper flakes, white pepper, and cumin. Cook for 3 minutes.
Pour the beef broth into the skillet and scrape up any browned bits. Stir in the tomato paste until smooth. Add the cooked beef and boiled potato, then remove from the heat and let the filling cool completely.
Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper. Divide the chilled dough into golf ball sized pieces. Roll each piece on a floured surface into a 5-inch circle, about 1/4-inch thick.
Place 2 tablespoons of the cooled filling in the center of each circle. Sprinkle with the scallions and cheese. Whisk the egg and 3 tablespoons (45 ml) of water in a small bowl. Brush the edges of the dough with the egg wash.
Fold the dough over to form a half-moon and crimp the edges tightly with a fork. Place the empanadas on the baking sheet and brush the tops lightly with the remaining egg wash. Bake for 20 minutes until golden brown.