Fry the minced meat in a saucepan with a little oil until crumbly, add the onions and season with pepper and paprika. Add the cream and milk, simmer a little. Season the sauce with about 1 1/2 teaspoons of instant stock. Let the processed cheese melt slowly in the sauce. Remove the pan from the heat and allow about 1/4 of the grated cheese to melt in the sauce. Season to taste, add salt if necessary.
Spread some of the sauce on the bottom in an ovenproof baking dish, then layer alternately potatoes and kohlrabi. Keep adding sauce between layers.
Place the casserole dish in the oven at 180 ° C and bake for about 30 minutes. About 10 minutes before the end, sprinkle the rest of the grated cheese over the top.