Wash cutlets, dab dry, season with salt and pepper. Whisk the egg in a deep dish. Put flour and breadcrumbs separately on 2 flat plates. Turn the schnitzel first in flour, then in egg and finally in breadcrumbs.
Wash the thyme, dab dry, pluck the leaves from the stalks. Peel cucumbers, halve, core and cut into strips. Clean and clean the mushrooms and, depending on their size, possibly halve or quarter them.
Peel and wash the potatoes and cook them in boiling salted water for about 20 minutes. Melt the fat. Fry the mushrooms for about 10 minutes over high heat, turning them over. Add cucumbers. Deglaze with vegetable stock, bring to the boil.
Stir in cheese and cream, season with salt, pepper and thyme and let simmer for about 4 minutes while stirring. Heat oil in a pan. Fry escalopes on each side for about 3 minutes until golden brown. Arrange potatoes, vegetables and schnitzel on plates.
Garnish with thyme and lemon.