01 - Preheat oven to 425°F.
02 - In a large bowl, toss the mushrooms with olive oil, garlic, thyme, salt, and pepper. Spread in a single layer on a baking sheet.
03 - Roast for 20–25 minutes, stirring once, until golden and tender.
04 - In a medium saucepan, bring water and milk to a gentle boil. Add salt.
05 - Gradually whisk in the polenta, stirring constantly to prevent lumps. Reduce heat to low and cook, stirring frequently, for 20–25 minutes, until thick and creamy.
06 - Stir in butter, Parmesan, and black pepper. Taste and adjust seasoning as needed.
07 - Divide the creamy polenta among bowls. Top with roasted mushrooms and sprinkle with parsley and extra Parmesan if desired. Serve immediately.