Melt 1 tablespoon of butter in a large pan over medium high heat. Add the mushrooms and cook for 5-6 minutes until tender and golden brown.
Add the garlic and cook for 30 seconds. Season the mushroom mixture with salt and pepper to taste and cover to keep warm.
While the mushrooms are cooking, make the risotto. Melt 1 tablespoon of butter in a large pot over medium high heat. Add the onion and cook for 2-3 minutes or until translucent.
Add the rice and cook for 2-3 minutes. Add the white wine and bring to a simmer. Cook until the wine has reduced by half.
Add 1 cup chicken broth; simmer over medium heat, stirring occasionally, until mostly absorbed, 4 to 5 minutes.
Continue to add broth, 1 cup at a time, stirring occasionally, until absorbed before adding more. Cook until rice is creamy and just tender, about 15-20 minutes (you may not need all the broth). Season to taste with salt and pepper.
Remove risotto from heat. Stir in mascarpone and parmesan cheeses.
Add 3/4 of the mushrooms into the risotto and stir to combine.
Place the remaining mushrooms on top of the risotto as a garnish. Sprinkle with parsley and serve.