Heat a large skillet over high heat. Add 2 tablespoons oil, swirling to coat. Add half the mushrooms, season with a large pinch of salt and pepper, and cook until golden and tender, 4 to 5 minutes. Transfer to a bowl and repeat, using 1 tablespoon oil. Add thyme to second batch, then transfer to bowl. Season with salt and pepper, and toss. Serve with crackers or crostini.