Peel, wash and quarter the potatoes and cook in boiling salted water for about 20 minutes. Clean, wash and cut the sprouts crosswise. Steam in a pot covered with a little water for about 10 minutes.
Meanwhile wash the meat, dab dry and cut into strips. Season meat with salt. Heat oil in a large pan. Fry the meat for 3-4 minutes on a high heat until golden brown. Remove the Brussels sprouts and let them drain briefly.
Remove meat from the pan. Add the Brussels sprouts and fry over medium heat for 3-4 minutes. Wash oregano, dab dry, put 1-2 stems aside for garnishing. Pluck the leaves of the remaining oregano from the stems.
Push the sprouts to the edge of the pan. Add honey and caramelise briefly at medium heat. Deglaze with vinegar, stock and 1 tablespoon butter. Add meat and oregano and simmer for 1-2 minutes, stirring continuously.
Season to taste with salt, honey and pepper if necessary. Drain and mash the potatoes, stir in the milk and 30 g butter. Season to taste with salt, pepper and nutmeg. Arrange in a preheated bowl and serve.