01 - Preheat the oven to 425°F for mushroom roasting.
02 - On a large baking sheet, toss mushrooms with olive oil, minced garlic, fresh thyme, salt, and pepper. Spread in a single layer for even roasting.
03 - Roast mushrooms for 20–25 minutes, stirring once halfway through cooking, until golden brown and tender.
04 - In a large saucepan, bring water and milk to a gentle simmer over medium heat.
05 - Slowly whisk in the coarse cornmeal, stirring constantly to prevent lumps from forming.
06 - Reduce heat to low and cook, stirring frequently, for 20–25 minutes until mixture thickens to a creamy consistency.
07 - Stir in butter, Parmesan cheese, salt, and pepper. Taste and adjust seasoning as needed.
08 - Spoon creamy polenta into bowls or plates. Top with roasted mushrooms and any pan juices. Garnish with chopped parsley and additional Parmesan if desired. Serve immediately.