Wash the meat, dab dry. Use a knife or poultry shears to divide the leg at the joint. Season all around with salt, pepper, paprika and spread a thin layer of oil. Cook in the preheated oven (electric cooker: 200 °C/ circulating air: 175 °C/ gas: level 3) for approx. 40 minutes.
For the gratin, peel and wash the potatoes and cut them into thin slices. Layer the potato slices in a small greased casserole dish. Season with salt and sprinkle with cream. Add the potato gratin to the meat in the oven for 30 minutes.
Peas in shell. Peel and chop the onion. Melt butter. Sauté diced onion for about 5 minutes until translucent. Add peas after 3 minutes. Add stock, bring to the boil and stew for about 5 minutes.
Wash the mint, shake dry, pluck leaves from the stalks and cut into strips, except for something to garnish. Add the mint to the peas 2 minutes before the end of the cooking time. Season to taste with salt and sugar.
Arrange on plates and garnish with mint.