In a heavy skillet melt half of the butter over medium heat. Add mushrooms and shallots and saute until tender, about 8 minutes. Add garlic, thyme sprigs, salt and pepper and stir for an additional minute. Remove mushroom mixture from pan and set aside.
Add remaining butter to pan over medium heat. Once melted, add rice and stir until rice begins to look translucent, 3-4 minutes.
Add ¾ cup dry white wine and lemon juice and bring to a simmer, stirring constantly until liquid is absorbed. Add mushroom stock or 1 cup of vegetable broth and stir until almost all broth is absorbed. Continuing adding broth 1 cup at a time, and stir until liquid is almost absorbed. (This step takes 20-25 minutes.)
Add mushrooms mixture into the rice and stir to combine. Gently stir in heavy cream and parmesan cheese and cook for an additional 5 min on low heat. Risotto should be creamy, but firm to the bite. Transfer risotto to a serving bowl and top with freshly ground pepper, shaved parmesan and fresh parsley.
