Easy Mushroom Gravy

Bahan-bahan (4 porsi)

• ¾ pound mushrooms (sliced)
• ¼ cup finely diced onion
• 3 tablespoons butter
• 1 clove garlic (minced)
• 2 tablespoons red wine (optional)
• 3 tablespoons all-purpose flour
• salt and pepper to taste
• 2 to 3 cups beef broth