01 - Heat olive oil and 1 tablespoon butter in a large heavy-bottomed skillet or Dutch oven over medium heat. Add onions and cook until translucent, about 3 minutes. Stir in garlic and cook for 1 minute more.
02 - Add sliced mushrooms and cook, stirring occasionally, until golden and liquid has evaporated, approximately 8 minutes. Season with ¼ teaspoon salt and a pinch of black pepper. Reserve half for garnish.
03 - Add Arborio rice to the skillet and toast, stirring constantly, until grains become lightly translucent around edges, about 2 minutes.
04 - Pour in dry white wine and cook, stirring, until mostly absorbed by the rice.
05 - Add 1 cup warm vegetable broth and stir gently until mostly absorbed. Continue adding broth in ½ cup increments, stirring frequently and allowing absorption between additions, until rice is creamy and al dente, approximately 18 to 22 minutes. Not all broth may be needed.
06 - Reduce heat. Stir in remaining 2 tablespoons butter, Parmesan cheese, heavy cream, and half of the chopped parsley. Adjust seasoning with remaining salt and pepper to taste.
07 - Spoon risotto into serving bowls. Top with reserved sautéed mushrooms and sprinkle with remaining parsley. Serve immediately.