Heat the oven to 220°C/Fan 200°C/Gas 7. Put the sundried tomatoes into a bowl and cover with boiling water. Set them aside to soak.
Peel and cut the sweet potatoes into wedges. Arrange them on a baking tray along with 2 whole, unpeeled garlic cloves. Drizzle over 1 tbsp olive oil. Season with salt and pepper and toss to coat. Roast for 30 mins.
Put the mushrooms into a large bowl or dish. Peel and finely chop the remaining garlic clove. Add to the mushrooms with 1 tbsp balsamic vinegar, the thyme leaves and 1 tbsp oil. Stir well to mix and set aside to marinate.
After 30 mins, take the sweet potatoes out of the oven and remove the garlic cloves. Halve the tomatoes. Add them to the tray. Return to the oven for a further 15 mins till the wedges are crisp on the outside.
While the veg roast, peel the roasted garlic cloves and finely chop them. Drain and chop the sundried tomatoes. Mix the garlic and sundried tomatoes in a bowl with 1 tbsp olive oil, 1 tbsp water and a good pinch of salt and pepper.
Set a large frying pan over a medium heat. When hot, add the marinated mushrooms. Fry for 8-10 mins, turning once or twice, till golden brown.
Serve the mushrooms with the sweet potato wedges, roasted tomatoes and salad leaves on the side. Drizzle over the tomato and garlic dressing.