Preheat Oven to 180°C (350°F/ Gas Mark 4).
In a large bowl/jug, pour the boiling water over the dried shiitake mushrooms and leave for at least 20 minutes.
Remove the mushrooms from the water, squeezing out any excess back into the water. Chop roughly and set aside. Crumble the stock cube into the water.
Heat an oven-proof pan or casserole with the oil over a medium hob. Cook the onion for 5 minutes until it softens then add the garlic and continue to cook for another minute.
Add the rice and stir to combine, continue cooking for 2 more minutes then increase the heat and add the wine. Boil rapidly until the wine has been absorbed and reduced away. Add the stock, thyme and umami seasoning and return to the boil. When the risotto reaches boiling point, cover and transfer to the oven.
Bake for 15-20 mins until most of the liquid has been absorbed and the rice is cooked (it should be fluffy on the outside but still al dente in the middle). Stir in the butter and serve garnished with some fresh thyme leaves.