Remove the stalks from 4 portobello mushrooms. Whisk together 2 tbsp olive oil, 1 tsp chopped thyme and 2 crushed garlic cloves. Brush the open sides of the mushrooms with the oil and grill for 5 minutes. Turn over, brush with more of the oil and cook for 5 minutes more. Turn over again, brush with more oil, then sprinkle with 2 tsp vegan parmesan cheese, either home-made or grated shop-bought. Grill until bubbling.