Preheat the oven at 70°C/ 160° C. While the oven is heating up, place your two serving plates and an oven dish inside to warm up.
Take the perch filets and season them well on both sides with salt and pepper. Place the flour in a shallow dish and dip the perch in the flour, coating both sides evenly. Shake off any excess.
Melt a small knob of butter together with the oil in a frying pan and sear the perch filets (flesh side down at first) for 1 minute. Then, flip over gently to fry on the skin side for a few seconds.
Take the preheated baking dish out of the oven and place the perch filets inside. Place them in the oven so they stay warm while we prepare the butter sauce.
For the butter sauce, melt the rest of the butter in the pan and heat it up until lightly browned. Sprinkle salt and add the white wine and parsley. Bring it to a gentle simmer for a minute and take it off the heat to steep for 5-10 minutes.
Divide filets between two warmed plates and serve with lemon slices on top and plenty of butter sauce. Enjoy!