Wash potatoes thoroughly and cook in boiling water for about 20 minutes. Peel carrots. Wash and clean the beans and halve them according to size. Cook the beans in boiling salted water for about 5 minutes. After about 3 minutes add the carrots. Peel onion and cut into strips
Cut the potatoes into slices. Pour oil into a hot ovenproof pan at the bottom approx. 24 cm, at the top approx. 28 cm (Ø). Fry the potatoes for about 15 minutes while turning. Add onion, carrots and beans and fry for another 10 minutes.
Beat the eggs. Season with salt and pepper. Grate cheese roughly and stir in. Pour the egg mixture into the pan and let it set at low heat until the edges become firm. Let the frittata fry in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for another 15 minutes until the egg mixture is firm and the frittata is golden brown.