01 - Preheat the oven to 425°F.
02 - In a large bowl, toss the sliced mushrooms with olive oil, garlic, thyme, salt, and pepper. Spread evenly on a baking sheet.
03 - Roast mushrooms for 20 to 25 minutes, stirring once halfway through, until golden and crisp at the edges.
04 - Bring the vegetable broth and milk to a gentle simmer in a large saucepan.
05 - Gradually whisk in the polenta. Reduce heat to low and cook, stirring often, until thick and creamy, about 20 minutes.
06 - Stir in butter, Parmesan, salt, and pepper. Adjust seasoning to taste.
07 - Divide the creamy polenta among bowls. Top with roasted mushrooms, sprinkle with parsley, and extra Parmesan if desired. Serve warm.