Clean, wash, drain and quarter the Brussels sprouts. Peel onions and cut into cubes. Heat the oil in a pan and fry the onions and Brussels sprouts lightly. Deglaze with stock, bring to the boil and braise covered for 8-10 minutes.
Caramelize sugar, 1 tablespoon water and chestnuts in a pan until golden brown. Remove from the pan immediately and spread on a sheet of baking paper. Clean the pan, heat the fat in it and fry the potato noodles until golden brown, turning them over.
Cut tomatoes into fine strips. Dice corned beef. Remove the lid from the Brussels sprouts pan. Let the rest of the liquid simmer until the Brussels sprouts start to fry lightly in the pan again.
Add corned beef, tomatoes and chestnuts, heat briefly and season with pepper.
Arrange potato noodles and sprouts on plates and sprinkle with parmesan and pepper.