Peel, wash and slice the potatoes. Put slices on a baking tray, drizzle with 1 tablespoon of oil, season with salt and mix. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) on the lower rack for 40-45 minutes.
Wash the pumpkin, grate dry and cut in half. Remove seeds and cut the pumpkin into slices. Wash the fillets, dab dry and remove thin skins. Season fillets with salt and pepper. Heat 1 tablespoon of oil in a wide saucepan or frying pan and fry the fillets all around for about 5 minutes.
Add half balsamic vinegar and 50 ml white wine and spread the fillets with apple jelly. Cover the roaster or pot and cook the meat for another 15-20 minutes at medium heat, adding the balsamic vinegar again and brushing with jelly.
Add the pumpkin to the potatoes about 15 minutes before the end of cooking and sprinkle with a tablespoon of oil. Wrap meat in aluminium foil and let it rest. Deglaze the meat with 150 ml white wine. Stir in crème légère, thicken slightly with sauce thickener and season to taste with salt and pepper.
Wash the thyme, remove the leaves from 4 stems and add to the vegetables. Season vegetables again with salt and pepper and arrange on a plate. Arrange the fillets on the vegetables and garnish with thyme.