1 lb (500g) chicken breast, cut into cubes1 medium onion, chopped2 cloves garlic, minced2 tablespoons oil7 oz (200g) sliced mushrooms1 cup tomato sauce1 tablespoon mustard2 tablespoons ketchup1 can (about 7 oz) heavy cream or table creamSalt and pepper to tasteChopped parsley for garnish