Clean and wash the zucchini and peppers. Peel the onion. Cut everything into small pieces. Melt the fat in a pot and fry the vegetables in it. Deglaze with 1/8 litre water, bring to the boil and stir in the broth.
Cover and braise at low heat for 10 minutes. In the meantime bring 1/2 litre of water to the boil, remove the pot from the heat and add the milk. Stir in the puree powder and let it swell for 1 minute.
Stir vigorously once again. Heat the oil in a pan and fry the sausages in it all around for about 5 minutes. Season with herbs from Provence. Stir the tomato ketchup into the ratatouille, braise again briefly and season with salt if necessary.
Serve mashed potatoes, ratatouille and sausages garnished with parsley.