01 - In a large, heavy-bottomed pot or Dutch oven, heat the olive oil and butter over medium heat. Add the finely chopped onion and sauté until softened, approximately 3 to 4 minutes.
02 - Stir in the minced garlic and cook for 1 minute until fragrant, ensuring it does not brown.
03 - Add the sliced mushrooms and thyme to the pot. Sauté for 6 to 8 minutes, allowing the mushrooms to brown and most of the released liquid to evaporate.
04 - Introduce the Arborio rice to the pot. Stir continuously for 1 to 2 minutes, coating the grains until they appear slightly translucent around the edges.
05 - Pour in the dry white wine. Stir and cook until the wine has been almost completely absorbed by the rice.
06 - Begin adding the warm vegetable broth, one ladleful (approximately 1/2 cup) at a time. Stir frequently, allowing each addition to be nearly absorbed before incorporating the next. Continue this process for about 18 to 20 minutes.
07 - Once the rice has reached a creamy, al dente consistency, stir in the heavy cream and grated Parmesan cheese. Season generously with salt and freshly ground black pepper to your preference.
08 - Remove the pot from the heat. Cover and let the risotto rest for 2 minutes to allow the flavors to meld.
09 - Serve the risotto hot, garnishing with fresh parsley and additional Parmesan cheese, if desired.