Finely chop or mix 1/3 of the cashew nuts. Coarsely chop the remaining kernels. Wash chicken fillets and dab dry. Whisk the egg in a bowl. Mix fine cashews and breadcrumbs in a bowl, put flour in a 2nd bowl. Season fillets with salt and pepper, first in flour, then egg and finally in breadcrumbs.
Heat 2 tablespoons of oil in a frying pan. Brown the fillets all around, then place them on a baking tray or in an ovenproof dish. Cook meat in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 10 minutes.
Roast the remaining cashew nuts in a pan without fat. Wash the spinach and drain well. Peel and finely chop the onion. Wash the tomatoes. Heat 1 tablespoon of oil in a frying pan. Fry the tomatoes and diced onion for 2-3 minutes, then add the spinach. Let the spinach collapse, season with salt, pepper and nutmeg
Remove meat from the oven and cut into slices. Arrange on the spinach and sprinkle with the cashew nuts