Cut the top off each garlic head; discard. Rub cut side of each garlic head with 1 teaspoon oil. Remove white papery skin from garlic heads (do not peel or separate the cloves). Wrap garlic in foil. Bake at 425° for 1 hour or until tender; cool 10 minutes. Separate cloves; squeeze to extract garlic pulp. Discard skins. Combine garlic pulp and 2 tablespoons Madeira in a bowl; mash with a fork.
Bring 1 1/2 cups stock to a boil. Add porcini; let stand 30 minutes or until soft. Drain through a colander over a bowl, reserving soaking liquid; chop porcini. Combine porcini liquid and remaining 3 1/2 cups stock; bring to a simmer in a medium saucepan (do not boil). Keep warm.
Heat a Dutch oven over medium heat. Add remaining 2 tablespoons oil; swirl to coat. Add onion to pan; sauté 5 minutes or until tender. Add cremini and shiitake mushrooms; cook 5 minutes or until browned, stirring occasionally. Stir in porcini. Add rice; sauté 1 minute, stirring constantly. Add remaining 1/2 cup Madeira; cook 1 minute or until liquid is absorbed. Stir in 1 1/2 cups stock; cook 4 minutes or until liquid is nearly absorbed, stirring constantly. Add remaining stock, 3/4 cup at a time, stirring constantly until each portion of stock is absorbed before adding the next (about 25 minutes total). Reserve 1/3 cup stock from the last addition. Remove pan from heat; stir in garlic mixture, remaining stock, cheese, salt, pepper, and chopped sage. Spoon into shallow bowls. Garnish with sage leaves, if desired.
I've made many risottos from CL and this one is one of my favorites. The roasted garlic really made it delicious. Make this, you won't regret it. I used sherry since I didn't have Madeira in the house.
Wonderful! Don't be afraid to taste and add additional liquid if your risotto hasn't achieved the desired creaminess just when you've nearly exhausted your addition of broth. I was hesitant to add the fresh sage at the end but it added remarkable flavor to this dish already loaded with Madeira, roasted garlic, porcini mushrooms, etc.