Coat a large saute pan generously with olive oil and add the smashed garlic cloves. Bring to a medium-high heat. When the garlic cloves have begun to brown and are very aromatic remove and discard them. Add the assorted fresh mushrooms to the pan and season with salt. Saute the mushrooms until they are soft and pliable. Turn off the heat and reserve.
Using your hand, carefully scoop the porcini mushrooms out of the hot water. (At this point the water should have cooled off significantly. If it is still too hot for your hand, use a slotted spoon.) Pour the top 2/3 of the mushroom water into another container and reserve for use while making the risotto. Discard the bottom third. It contains a lot of sand and dirt from the mushrooms. Puree the rehydrated mushrooms with a little of the reserved mushroom water to make a smooth mushroom paste. This will not look good but it will certainly taste good! Reserve.
Coat a large saucepot abundantly with olive oil. Add the onions and season generously with salt. Bring the pot to a medium-high heat. Cook the onions, stirring frequently until they are very soft and aromatic but have no color. Add the rice and stir to coat with the olive oil. Cook the rice for 2 to 3 minutes to toast, stirring frequently. Add wine to cover the surface of the rice and stir frequently until it has completely absorbed. Add the reserved mushroom water and then add chicken stock until the liquid has covered the surface of the rice. Stir frequently until the stock has absorbed into the rice. Repeat this process 2 more times. Check for seasoning, you probably will need to add salt.
During the third addition of stock, add the reserved sauteed mushrooms and 2 tablespoons of the pureed porcini mushrooms. When the stock has absorbed into the rice and the rice is cooked but still "al dente", remove the pot from the heat. Add the butter and cheese and whip until well combined. This will set the perfect consistency of the rice. The rice should flow and not be able to hold its shape and look very creamy. Serve immediately garnished with chives.