Preheat your oven to 400°F (200°C).

Clean the mushrooms by wiping them with a damp paper towel to remove any dirt. Trim the stems if necessary and place them in a large mixing bowl.

In a small saucepan, melt the butter over medium heat. Add the minced garlic and sauté for about 1-2 minutes, until fragrant and lightly golden, but not browned.

Pour the garlic butter over the mushrooms in the bowl. Add the thyme, salt, and pepper. Toss well to ensure all mushrooms are evenly coated.

Spread the mushrooms in a single layer on a baking sheet lined with parchment paper.

Roast in the preheated oven for 20-25 minutes, tossing halfway through, until the mushrooms are golden brown and tender.

Remove from the oven and drizzle with lemon juice if desired. Garnish with fresh parsley before serving.