Using a sauté pan, heat the olive oil over medium-high heat. Add in the mushrooms and sauté until the mushrooms are softened, about 5 to 8 minutes. Season with salt and pepper.
While your bread slice is still hot from the toaster, rub on the garlic. Spread on some butter if desired. Top with the sautéed mushrooms and drizzle balsamic glaze over the top. Sprinkle chives and Maldon sea salt flakes to finish. Enjoy!