Peel and finely chop the onion. Wash the tomatoes and grate them coarsely on a kitchen grater. Heat the oil and fry the onion. Sprinkle curry on top, add tomatoes and ketchup. Season with salt and pepper.
Let it simmer at medium heat for 10-15 minutes. Place the potato wedges on a baking tray. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 20 minutes.
Clean, wash and cut the peppers into pieces. Clean and wash the mushrooms. Cut curry sausages into pieces of about 5 cm. Put sausage, paprika and mushrooms alternately on skewers. Grill on the hot grill for about 8 minutes while turning.
Season the sauce again. Serve skewers with potato wedges and sauce, dust with curry.