Peel onion and carrot. Wash, clean, quarter and seed the tomatoes. Cut prepared ingredients into small cubes. Heat oil. Fry the diced onion and carrot for 4 minutes until transparent.
Add tomato cubes and season with salt and pepper. Wash and chop the herbs. Mix ricotta, chopped herbs and egg. Season with salt and pepper. Pour into a piping bag with a large perforated spout and squirt into the cannelloni.
Melt butter and sweat flour in it. Deglaze with stock and cream, bring to the boil while stirring constantly. Season with salt and pepper as well. Place the sauce, cannelloni and steamed vegetables alternately in an ovenproof dish.
Sprinkle with grated Parmesan and cook in the preheated oven (electric cooker: 175 °C/ circulating air: 150 °C/ gas: level 2) for about 40 minutes.