01 - Preheat the oven to 425°F for roasting the mushrooms.
02 - In a large bowl, toss the sliced mushrooms with olive oil, minced garlic, fresh thyme leaves, salt, and pepper until evenly coated.
03 - Spread the seasoned mushrooms evenly on a baking sheet. Roast for 20–25 minutes, stirring once halfway through, until golden brown and crisp at the edges.
04 - While mushrooms roast, combine vegetable broth and whole milk in a large saucepan. Bring to a gentle simmer over medium heat.
05 - Gradually whisk in the coarse cornmeal, ensuring no lumps form. Reduce heat to low and cook, stirring frequently, for 20 minutes until the mixture thickens and becomes creamy.
06 - Remove from heat. Stir in unsalted butter, grated Parmesan cheese, salt, and pepper. Adjust seasoning to taste.
07 - Divide the creamy polenta among serving bowls. Top with roasted mushrooms and sprinkle with fresh chopped parsley. Add extra Parmesan if desired. Serve immediately while warm.