Combine the minced meat, one diced onion, salt, pepper, and hot paprika powder. Shape into meatballs. Heat margarine in a large frying pan over medium-high heat and fry the meatballs for 8-10 minutes until browned on all sides. Transfer the meatballs and pan drippings to a baking dish. Peel the boiled potatoes, cut into slices, and arrange them around the meatballs.
Heat 1-2 tablespoons of margarine in a separate pan over medium heat. Add the second diced onion and cook for 3-4 minutes until softened. Dust with 2 tablespoons of flour and stir for 1 minute. Slowly pour in the broth while stirring constantly, then stir in the crème fraîche. Season to taste with salt and pepper.
Pour the sauce over the potatoes and meatballs. Sprinkle grated cheese over the top. Bake in a preheated oven at 225°C (437°F) for 40 minutes until the meatballs reach an internal temperature of 63°C (145°F) and the cheese is golden.