Defrost the peas. Peel, halve or quarter potatoes and cook in boiling salted water for about 20 minutes. Wash the meat, dab dry and cut diagonally into thick strips.
Season with salt and pepper. Whisk the eggs in a deep dish. Mix breadcrumbs and oatmeal. Turn the meat in flour one after the other, pull it through the egg and turn it in the oatmeal and breadcrumbs mixture, pressing it down a little.
Heat the oil in a frying pan. Fry the chicken pieces in it in portions for about 5 minutes, turning them over until brown. Keep finished pieces warm. Wash the parsley, dab dry, pluck the leaves from the stalks and chop finely except for a little garnish.
Peel onion and cut into rings. Heat 1/2 tablespoon butter in a pot. Fry the onion rings in it. Add peas and broth, bring to the boil and stew covered for 1-2 minutes. Season to taste with salt, pepper and sugar.
Stir in the parsley. Drain the potatoes and let them evaporate briefly on the switched off hotplate. Add milk, add 1/2 tbsp. butter and mash to puree. Season to taste with salt, pepper and nutmeg.
Arrange mashed potatoes, peas and meat, garnish with parsley.