Place dried porcinis and stock or broth in a saucepan and bring stock to a boil. Reduce heat to low and simmer.
In a large skillet, heat oil and butter over medium to medium high heat. Add shallots and saute 2 minutes. Add arborio rice and saute, 2 or 3 minutes more. Add Sherry and cook the liquid completely absorbed. Add several ladles of hot stock or broth and reduce heat slightly. Simmer, stirring frequently until liquid is absorbed.
Remove mushrooms from water and reserve cooking liquid. Coarsely chop the porcinis and add them to the rice. Continue to ladle broth into arborio, half the remaining amount at a time. Stir mixture each time you add broth and remove from heat when the rice is cooked to al dente. Cool and store any remaining liquids if there are any.
The ideal total cooking time for perfect risotto is 22 minutes. The consistency should be creamy.
Stir in thyme and a few handfuls of grated cheese. Season your risotto with salt and pepper to your taste. Serve creamy mushroom risotto from the hot pan with warm, crusty whole grain breads.