To make the risotto: In a medium saucepan, heat the vegetable stock until steaming hot and maintain the heat throughout the cooking process.
In a Dutch oven, heat the olive oil over medium heat. Add the shallots, and allow them to sweat until translucent, about 4 minutes.
Add the rice to the Dutch oven and stir, allowing the grains to toast a bit on the bottom of the pan but not to brown, for about 2 minutes.
Add the wine to the rice slowly and stir to combine.
Ladle about ½ cup of the hot vegetable stock over the rice. Stir a couple times and let the grains settle. Stir again and allow the rice to soak up the stock for about 1 to 2 minutes. Repeat until all of the hot stock has been used.
Remove the risotto from the heat, let rest for 1 to 2 minutes, and then stir in the buttermilk, butter, cheese, and chives. Season with salt and black pepper and set aside.
To make the mushrooms: In a medium sauté pan, heat the olive oil over high heat. Gently add the mushrooms and sauté, tossing the mushrooms, until they’re seared on all sides, about 7 to 10 minutes.
Add the garlic and butter. Allow the butter to brown and foam.
Add the thyme, and baste the mushrooms with the butter for about 30 seconds.
Transfer the mushrooms to a paper towel-lined plate to drain.
Serve the mushrooms over the risotto, and garnish the dish with a drizzle of brown butter, Parmesan, and chives.