Heat 1 tbsp of the butter in a frying pan over a medium heat, until foaming. Add the mushrooms and fry for 3-4 minutes. Drain off any excess liquid and set the mushrooms aside. Return the pan to the heat, add the onion, garlic and remaining butter and cook for 5 minutes. Add the rice and stir for 1 minute. Add the wine and simmer until reduced to almost nothing. Add a ladleful of stock and simmer until nearly absorbed. Keep adding the stock in this way, until the rice is al dente – about 20 minutes. Fold in the thyme and mushrooms. Season, cool slightly, then chill until cold. Shape the risotto into 12 cakes. Make a hole in the centre of each and press in a piece of cheese. Cover by squeezing the sides together. Roll the risotto cakes in the flour. Heat the sunflower oil in a large frying pan and fry the cakes, in batches, for 3-4 minutes each side or until golden and crisp. Remove with a slotted spoon and drain on kitchen paper. Keep warm in a low oven while you fry the rest.
Serve 2-3 risotto cakes each, with a little dressed watercress and a spoonful of your favourite chutney.