Mix the flour, cayenne pepper and paprika together and coat the pork cubes with it.
Heat the oil and gently fry the pork pieces with the onion for 3 – 4 minutes. Stir in any remaining flour and spice mixture. Add the milk slowly, bit by bit, and stir over medium heat until the sauce thickens.
Simmer until the sauce is smooth and the pork cubes just cooked through (not overcooked).
Add the apple puree and grapes or mushrooms an simmer over gentle heat for another 12 – 15 minutes. Remove from heat, check seasoning and stir in the sour cream and yoghurt.
Serve with ribbon noodles.