I make it with buckwheat, wheat, or millet porridge.
Just like with a casserole. In this case, I mix the porridge with eggs, grated cheese, sour cream (a thicker, tangier version of sour cream common in Eastern European cuisine), and butter.
I serve krupnik with sour cream or milk.
For 500g of porridge, use 2-3 eggs, 250g of cheese, 300g of sour cream, 100g of butter, and sugar to taste.