Peel and wash the potatoes. Cook in boiling salted water for about 20 minutes. Cut sausages and gherkins into slices. Wash, clean and chop the tomatoes. Peel onion, cut into sticks and fry in hot oil.
Add cream, bring to the boil once and stir in the sauce thickener. Add sausage slices, gherkins and tomato and heat up as well. Season ragout with salt and pepper. Sprinkle with chopped parsley if necessary.
Drain the potatoes and eat with the ragout.