1 tablespoon butter
1 tablespoon olive oil
1 pound button mushrooms, sliced
2 medium onions, sliced
3 cloves garlic, chopped
2 teaspoons dried thyme
1 (750 milliliter) bottle red wine
1 (14.5 ounce) can beef broth
1 tablespoon white sugar
1 pinch salt and pepper to taste
Heat the butter and olive oil in a large skillet over medium heat. Add the onions; cook and stir until translucent, 5 to 10 minutes. Stir in the garlic and thyme; cook and stir for a few minutes, then add the mushrooms. Cook for about 8 minutes, stirring occasionally, until the liquid from the mushrooms evaporates.
Pour in the whole bottle of wine and the beef broth. Bring to a boil, then reduce the heat to medium and stir in the sugar. Cook, stirring occasionally, until the liquid is almost entirely gone, about 1 1/2 hours. Season with salt and pepper. Serve as a side, or topping for steaks or crostini.