Stuffed Portobello mushrooms with caramelised Brussels sprouts

Name: Stuffed Portobello mushrooms with caramelised Brussels sprouts
Prep time: 15 min
Cook time: 1 h
Total time: 1 h
Yield: 6 portions
Ingredients: 6 fresh portobello mushrooms; 240 g water; 220 g full cream milk; 2 tsp olive oil; 2 dried bay leaves; ½ tsp dried thyme; 1 tbsp Vegetable stock paste; 100 g polenta; 1 - 2 pinches sea salt; ½ tsp ground black pepper; 100 g mascarpone cheese; 8 Brussels sprouts; 1 garlic clove; 120 g red onion; 20 g unsalted butter; 1 tbsp dark brown sugar; 1 tbsp balsamic vinegar; ½ tsp sea salt