Heat a small knob of the butter in a pan, add the mushrooms and ½ tsp salt, and cook until tender and golden (it will seem like a lot of mushrooms at first but they will eventually cook down). Add the rest of the butter, garlic and rosemary, and cook gently for 4-5 minutes. Stir in the paprika and season with black pepper then keep on a low heat while you cook the gnocchi following pack instructions. Drain the gnocchi then tip into the mushroom pan and toss. Serve in warm bowls with a dollop of soured cream, lots of black pepper and a grating of parmesan, if you like.