Warm bone stock over low heat in a small saucepan. Set aside.
In a heavy skillet melt 4 tbsp butter over medium heat. Add mushrooms and shallots and cook until tender, about 8 minutes. Add garlic, thyme, salt and pepper and stir for another 1-2 minutes. Remove mushroom mixture from pan. Set aside.
In another pan, add remaining butter to pan over medium heat. Once melted, add rice and stir until rice begins to look translucent, 3-4 minutes.
Add white wine and lemon juice and bring to a simmer, stirring constantly until liquid is absorbed. Add 1 cup of bone stock and stir until almost all broth is absorbed. Continuing adding broth 1 cup at a time, and stir until liquid is almost absorbed. (this takes 20-25 minutes.)
Add mushrooms mixture into the rice and stir to combine. Gently stir in heavy whipping cream and parmesan cheese and cook for an additional 5 min on low heat. Texture should be creamy, but with a firm bite. Garnish with ground pepper, grated parmesan, fresh parsley and serve.