Dice the onion, finely chop the garlic and slice the mushrooms. Cut the sausages into diagonal slices. Heat the oil and fry the sausage slices over a medium heat until golden brown all over. Briefly fry the onion and garlic, add the mushrooms and fry together. Pour in the cream and soup, stir in the mustard and simmer over a low heat for approx. 10 minutes until the sauce is creamy. Season to taste with salt and pepper. Serve garnished with parsley.