Spread the walnuts out on a baking tray, and bake for 10-15 minutes, tossing occasionally, until golden and toasted. Set aside.
Pour the 1.5 cups boiling water over the dried porcini in a bowl and let rehydrate for 10 minutes or so.
Oil the tray and add your mushrooms, and four cloves of garlic (unpeeled). Drizzle with olive oil and sprinkle over salt and thyme leaves.
Turn the oven up to 200C, and add mushrooms. Roast for 15 minutes or so until golden brown and releasing their juice. Toss with one tablespoon of the butter, add a little more salt, and set aside.
While the mushrooms are roasting, heat some olive oil and a tablespoon of the butter in a large pot over medium-low heat. Add the leek, two cloves of garlic, and the rehydrated porcini. Saute 5 minutes or so.
Into a small pan, heat the stock and the porcini water. Add the stems from the mushrooms that are in the oven.
When the leek and garlic is soft, add the rice. Cook for about 2 minutes, stirring to coat the rice in the oil.
Add the wine, and stir until absorbed.
Keep adding the stock a ladleful at a time, until all is absorbed and the rice is soft (about 20-25 minutes).
I like to add some fresh thyme about halfway through, throwing the stems into the simmering stock.
Just before serving, chop the mushrooms and add to the risotto. Keep stirring until they are warmed through, then throw in a few more sprigs of thyme. Add the last of the butter, and the parmesan-style cheese. Check for seasoning – depending on your stock, you might need to add a fair bit of salt and always a good crack of black pepper.
Serve warm with a drizzle of olive oil, and the chopped roasted nuts sprinkled over, alongside the goat cheese and a few fresh sprigs of thyme.