Wash the potatoes thoroughly and cook in plenty of boiling water for 15-20 minutes. Peel onions and cut into strips. Bring the stock to the boil. Add vinegar and oil, bring to the boil. Add onions. Drain potatoes, rinse and peel.
Halve potatoes if necessary. Mix the warm marinade with the potatoes and let it soak well. Wash chicken legs, dab dry and season with salt and pepper. Crumble toast very finely. Put flour and crumbs separately in deep plates. Beat the eggs in a deep plate. Turn chicken legs first in flour, then in egg and finally in bread crumbs. Heat the frying fat in a deep fryer to 180 °C and bake the chicken legs in 2 portions one after the other for 15-20 minutes. Turn them in between and finally test them with a wooden skewer. (When the meat juice is clear, the chicken is cooked). Keep the finished pieces warm in the oven. Clean and wash the watercress and remove the leaves. Mix into the potatoes and season to taste with salt, pepper and possibly a little vinegar.
Turn chicken legs first in flour, then in egg and finally in bread crumbs. Heat the frying fat in a deep fryer to 180 °C and bake the chicken legs in 2 portions one after the other for 15-20 minutes. Turn them in between and finally test them with a wooden skewer. (When the meat juice is clear, the chicken is cooked). Keep the finished pieces warm in the oven. Clean and wash the watercress and remove the leaves. Mix into the potatoes and season to taste with salt, pepper and possibly a little vinegar. Arrange fried chicken and salad on plates. Garnish with lemon slices