For extra flavor, sauté the diced mushrooms with a little butter and garlic before adding them to the burger mixture. If you don't have a food processor, you can finely chop the bread or use pre-made breadcrumbs. To prevent the patties from sticking to the grill, make sure the grates are clean and well-oiled. These burgers can also be cooked in a skillet over medium heat or baked in the oven at 375°F (190°C) for 20-25 minutes.