Clean and wash the peppers and spring onions. Cut vegetables into 3-4 cm pieces, sausage into thick slices and halve. Put the vegetables and sausage alternately on skewers and fry them all around in hot oil.
Remove from the pan and keep warm. Cut onions into rings. Fry in half the fat until golden brown and remove. Wash parsley, dab dry and, except for a little bit for garnishing, cut into small pieces and fry in the remaining hot fat.
For the mashed potatoes boil 1/4 litre of water. Remove the pot from the heat and stir in the mashed potatoes. Let stand for 1 minute and stir again. Arrange skewers and mashed potatoes on a preheated plate.
Add parsley butter and roasted onion rings to the purée. Garnish with remaining parsley and sprinkle with coloured pepper.