Peel, wash and halve the potatoes and cook in boiling salted water for about 15 minutes.
For the sauce, peel and finely chop 1 onion and garlic. Put the canned tomatoes in a high mixing bowl and puree. Heat 1 tablespoon of olive oil in a saucepan. Fry the onions and garlic for 2-3 minutes.
Deglaze with pureed tomatoes, bring to the boil and simmer for 6-7 minutes. Season to taste with salt, pepper and sugar.
Peel 1 onion and cut into fine cubes. Wash 4 stems of basil, shake dry and cut very finely. Knead minced meat, egg, breadcrumbs, onion and basil. Season with salt and pepper and form about 8 small meatballs.
Heat sunflower oil in a large frying pan. Fry the meatballs for 8-10 minutes at medium heat, turning them over. Drain the potatoes and let them drain well.
In the meantime clean, wash and halve the sugar snap peas. Clean, wash and cut spring onions into pieces of about 4 cm. Wash cherry tomatoes, grate dry and cut in half. Heat 2 tablespoons of olive oil in a second pan.
Fry the potatoes for about 10 minutes while turning. 3-4 minutes before the end of the frying time, add mangetouts and spring onions. Approx. 2 minutes before the end of the frying time, add the cherry tomatoes to the pan and flip them through briefly.
Season to taste with salt and pepper.
Remove the meatballs from the pan and place them on a baking tray lined with baking paper. Drain the mozzarella, place it between kitchen paper and squeeze it lightly so that the liquid escapes.
Cut mozzarella into 8 slices and place 1 slice on each meatball. Bake the meatballs in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for 5-6 minutes.
Add tomato sauce to the vegetables and heat briefly. Wash the remaining basil, shake dry and cut into fine strips. Take the meatballs out of the oven and add 1 tsp. pesto each. Arrange 2 meatballs and 2 tomato vegetables on plates.
Sprinkle with basil.