Wash potatoes thoroughly and cook in boiling water for about 20 minutes. Then drain, rinse, peel and slice the potatoes. In the meantime clean, wash and drain the spinach. Peel and finely chop the onions. Peel garlic and chop finely.
Heat the oil in a large pot and fry the onions until transparent. Add garlic and fry briefly. Add spinach, pour on 100 ml broth, bring to the boil and let it collapse. Season with salt and pepper. Pour into a sieve and drain. Wash, clean and slice the tomatoes. Cut mozzarella into slices. Grease an oven dish, layer potatoes, sprinkle with salt. Spread spinach on top, cover with tomatoes, season again with salt and pepper. Place the mozzarella on top and bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 25-30 minutes.
Wash, clean and slice the tomatoes. Cut mozzarella into slices. Grease an oven dish, layer potatoes, sprinkle with salt. Spread spinach on top, cover with tomatoes, season again with salt and pepper. Place the mozzarella on top and bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 25-30 minutes. In the meantime, wash the basil, shake dry and cut into strips. Garnish casserole with basil
Variation: Serve sprinkled with coloured pepper