Heat 1 tablespoon of oil in a flat frying pan and fry the meat on all sides for about 5 minutes. Continue cooking in the preheated oven (electric cooker: 150 °C/ convection oven: 125 °C/ gas: stage 1) for approx. 15 minutes.
For the vinaigrette, peel the onion. Peel and wash the celery. Wash the apple and grate dry. Finely dice onion and celery. Cut apple into slices from the core and dice. Heat 2 tablespoons of oil in a frying pan. Fry the diced onion and celery for about 4 minutes while turning. Add apple cubes and deglaze with stock. Season to taste with vinegar, mustard, salt and pepper
Cut meat into thin slices and arrange on a plate with vinaigrette. Roasted baguette bread tastes good with it