Clean the Brussels sprouts, removing the outer leaves. Cut the stalk thinly and cut the florets cross-shaped at the cut. Halve the large florets. Cook the Brussels sprouts in boiling salted water for 8 to 10 minutes, drain and drain well. Cut the bacon slices into thin strips. Halve the chestnuts depending on their size. Fry the bacon in a pan until crispy. Add butter and melt. Add chestnuts and a pinch of sugar and fry for 2 minutes. Mix in the Brussels sprouts and season with a little salt and pepper.