Combine 1-1/2 cups boiling water and mushrooms; let stand 10 minutes or until soft.
Drain through a colander over a bowl.
Reserve 1-1/4 cups soaking liquid; chop mushrooms.
Bring reserved soaking liquid and broth to a simmer in a small saucepan (do not boil).
Keep broth mixture warm over low heat.
Coat large saucepan with cooking spray and heat over medium-high heat.
Add rice, shallots, and garlic to pan; sauté 5 minutes.
Add wine; cook until liquid evaporates (about 2 minutes).
Add 1 cup broth mixture to rice mixture; cook over medium heat 5 minutes or until the liquid is nearly absorbed, stirring occasionally.
Add remaining broth mixture, 1/2 cup at a time, stirring occasionally until each portion of broth mixture is absorbed before adding the next (about 25 minutes).
Add mushrooms, Parmigiano-Reggiano and mascarpone cheeses, thyme, salt, and pepper.
Stir gently just until cheeses melt.
Add the half and half if you prefer.
Serve warm.
Provide extra mascarpone and Parmesan cheeses for guests to top their risotto if desired.
Calories: 198 for 1 cup serving