Peel, wash and roughly dice the potatoes and celery. Cover and cook in salted water for about 20 minutes.
Rinse the chanterelles, dab dry and clean. Peel and chop the onion. Wash the pike-perch fillet, dab dry and cut into 4 pieces. Wash sage and shake dry.
Drain the potatoes and celery. Add milk and butter and crush everything finely. Season to taste with salt and nutmeg. Keep warm.
Fry the bacon in a large pan without fat until crispy. Fry the onion and sage briefly, remove everything. Heat 2 tablespoons of clarified butter in the bacon fat. Fry the chanterelles for 4-5 minutes while turning.
Add the bacon mixture again. Season with salt and pepper.
Salt the fish and press it with the skin side into the flour. Tap off excess flour. Heat 1-2 tablespoons of clarified butter in a second pan. Fry the fish for about 3 minutes on the skin side first, then 1-2 minutes on the meat side.
Dress everything.