Step 1
Preheat oven to 180° C.
Step 2
Put chicken pieces in a bowl. Add salt and crushed peppercorns and mix well.
Step 3
Heat 3 tablespoons oil in a non-stick pan.
Step 4
Coat chicken pieces with flour and shallow-fry on high heat, turning sides, till golden brown on both sides. Transfer into an ovenproof baking dish.
Step 5
Heat remaining olive oil and 1 tablespoon butter in the same pan. Add onion, garlic and celery and sauté for 1 minute.
Step 6
Add mushrooms, salt and crushed peppercorns, mix and cook for 1 minute. Spread the mixture over the chicken pieces in the dish.
Step 7
To make sauce, heat 1 tablespoon butter in the same pan. Add 1 tablespoon flour and sauté till light brown.
Step 8
Add chicken stock and whisk well so that no lumps remaining and cook till the sauce thickens. Add salt, crushed peppercorns, lemon juice and parsley and mix well.
Step 9
Add cream, mix well and pour over the mushrooms.
Step 10
Mix together potatoes, remaining butter, parmesan cheese powder, salt, crushed peppercorns, thyme and oregano in a bowl. Spread this mixture over the sauce in the dish, place the dish in the preheated oven and bake for 15-20 minutes.
Step 11
Serve hot.