In a small bowl, combine the porcini mushrooms and ½ cup hot water. Soak for 30 minutes to soften. Drain the mushrooms, reserving the liquid, then chop the mushrooms. Place the stock in a saucepan and bring just to a simmer.

In a large saucepan over medium heat, melt 2 tablespoons of the butter with the olive oil. Add the onion and sautué until tender and translucent, about 5 minutes.

Add the mushrooms, thyme and cook, stirring, about 4 minutes. Stir in the rice and cook, stirring, until the kernels are hot and coated with oil, about 2 minutes. Add the wine and continue to cook, stirring often, until the liquid is absorbed.

Add the stock mushroom liquid and vegetable stock, ½ cup at a time, stirring constantly and making sure the liquid has been absorbed before adding more. When the rice is about half cooked, season with salt and pepper. The risotto is done when the rice grains are creamy on the outside, and firm, yet tender to the bite, 20 to 25 minutes. Rice varies, so you may not need all the stock, or you may need more. If more liquid is required, use hot water.

Remove the risotto from the heat. Stir in the remaining butter and the cheese. Spoon the risotto into bowls and serve immediately.