1. Sauté the Mushrooms

In a large skillet, melt the butter and olive oil over medium heat. Add the sliced mushrooms and cook for 5–7 minutes, stirring occasionally, until the mushrooms release their moisture and begin to brown.

Add the minced garlic, thyme, salt, and black pepper. Cook for another 2–3 minutes, stirring frequently, until the garlic is fragrant and the mushrooms are golden.

(Optional) Deglaze the skillet with white wine or vegetable stock, scraping up any browned bits from the bottom of the pan. Let the liquid simmer until mostly evaporated, about 1–2 minutes. Remove the skillet from heat and set the mushrooms aside.

2. Prepare the Bread

Spread one side of each slice of bread with a thin layer of softened butter. Place the bread butter-side down on a clean surface.

On the unbuttered side, layer one slice of cheese, followed by a generous scoop of the garlic mushroom mixture. Top with another slice of cheese, then place a second slice of bread on top, butter-side up. Repeat with the remaining slices to assemble all the sandwiches.

3. Cook the Sandwiches

Heat a large skillet or griddle over medium-low heat. Place the sandwiches in the skillet (work in batches if needed) and cook for 3–4 minutes on one side, pressing gently with a spatula. Flip carefully and cook for another 3–4 minutes on the other side, until the bread is golden brown and the cheese is fully melted.

Adjust the heat as necessary to prevent the bread from burning while ensuring the cheese melts evenly.

4. Slice and Serve

Remove the sandwiches from the skillet and let them cool for 1–2 minutes. Slice each sandwich in half and garnish with fresh thyme, if desired. Serve immediately with a side of tomato soup or your favorite dipping sauce.