Stir-fry brussels sprouts with mushrooms

From The Vegetarian Cookbook

• 1 tbsp oil
• 350 g brussels sprouts, prepared and thinly sliced
• 1 small onion, finely sliced
• 200 g oyster or shiitake mushrooms, sliced
• 1 tbsp soy sauce
• 50 ml Vegetable stock
• 1 tsp whole grain mustard
• 1 tsp cornflour
• 1 tbsp balsamic vinegar

In a wok, heat the oil and stir-fry the sprouts and onion for 2 minutes. Add the mushrooms, and continue to fry for another minute, then add all the remaining ingredients. Stir until the sauce thickens, serve.