Finely dice the bacon. Clean the mushrooms, wash them briefly if necessary and rub them dry. Cut mushrooms into thin slices. Wash thyme, shake dry, put 2-3 stems aside for garnishing. Pluck the leaves from the remaining stems
Peel the potatoes, wash them thoroughly and halve them depending on size. Cook in boiling salted water for about 25 minutes. In the meantime, wash the lemon, grate dry and finely grate the peel. Heat 2 tablespoons of oil in a frying pan and fry the meat on each side for about 2 minutes. Season with salt and pepper. Remove from the pan, place on a baking tray lined with baking paper and bake in a preheated oven (electric cooker: 100 °C/ convection oven: 75 °C/ gas: see manufacturer) for approx. 15 minutes.
In the meantime, leave the bacon in a pan until crispy and take it out. Add 2 tbsp. oil and 25 g butter to the pan, heat up. Add the mushrooms and fry well while turning. Add lemon zest and about 3/4 of the thymain leaves, fry briefly. Season mushrooms with salt and pepper, add bacon again
Heat milk and 50 g butter. Drain the potatoes, mash them with a potato masher, let the milk mixture run in and season with salt and nutmeg. Arrange the meat and mushrooms on a serving plate, sprinkled with some thyme leaves. Mash potatoes in a bowl with the rest of the thymain garnished extra