Place the dried mushrooms in a small heatproof bowl and pour over enough boiling water to cover well. Set aside for 20 minutes to soak.
Put your stock in a saucepan and keep warm on the hob.
In a large non-stick casserole, melt the butter, add the finely sliced leeks and diced celery and cook gently for 8-10 minutes until softened. Add the grated garlic and cook for a further couple of minutes.
Stir in the rice and coat in the butter and oil. Turn up the heat to medium-high, pour in the wine and bubble until almost reduced to nothing.
Add the warm stock a ladle at a time, stir the rice until absorbed and repeat. This should take around 25 minutes for the rice to be al dente - cooked, but still with a little bite.
In the meantime, in a medium saucepan, add 25g butter and add in the remaining clove of grated garlic and 1 tsp of the fresh thyme leaves. Cook for a minute, then add in your thickly sliced mushrooms. Cook the mushrooms, stirring occasionally, for around 5 minutes until they have softened, but make sure not to cook out all those lovely juices.
Strain the liquid from the dried mushrooms into your risotto pan, then finely chop the hydrated dried mushrooms.
When the risotto is almost done, add in the cooked mushrooms and the finely chopped hydrated mushrooms.
Stir in 25g of finely grated parmesan, have a final taste and adjust seasoning, then serve alongside the remaining 25g parmesan to sprinkle on top and the parsley if using.