Prepare the Mushrooms:
Clean the mushrooms with a damp paper towel or a soft brush to remove any dirt. Trim the stems if necessary and slice the mushrooms evenly (about 1/4-inch thick).

Heat the Pan:
In a large skillet or sauté pan, heat the butter or olive oil over medium-high heat until melted and hot.

Cook the Mushrooms:
Add the sliced mushrooms to the pan in a single layer. Allow them to cook undisturbed for about 2-3 minutes, allowing them to brown slightly on one side.

Season and Stir:
Once the mushrooms have browned on the first side, stir them gently to ensure they cook evenly. Add the minced garlic, salt, pepper, and thyme (if using). Continue cooking for another 4-5 minutes, stirring occasionally, until the mushrooms are tender and browned to your liking.

Deglaze (Optional):
If desired, pour in the white wine or vegetable broth to deglaze the pan. Scrape up any brown bits from the bottom of the pan and let the liquid cook down for an additional 1-2 minutes. This step adds more flavor and creates a slightly saucy finish.

Finish and Garnish:
Once the mushrooms are fully cooked and golden brown, remove the pan from heat. Taste and adjust seasoning if needed. Garnish with freshly chopped parsley before serving.