Heat the corn oil in a skillet, then dice the smoked bacon and fry it for 2–3 minutes until it turns golden brown.
Rinse the Brussels sprouts, trim them if necessary, and cut in half. Wash any wax off the orange and grate the zest into the skillet with the bacon and add the butter,mustard, and sprouts. Cook over a moderate heat for 5 minutes, stirring, until the sprouts are crisp.
Meanwhile, drain and roughly chop the water chestnuts, stir them into the sprouts, and cook them for 3–4 minutes until the sprouts are golden and the chestnuts are heated through. Add salt and black pepper to taste and serve.