Food & Cooking Recipes Lunch Recipes Portobello Mushroom Burger with Spicy Avocado Sauce 3.7 (29) 3 Reviews By Martha Stewart Test Kitchen Martha Stewart Test Kitchen The recipes developed by our test kitchen team have undergone a rigorous process of development and testing, ensuring that every element is optimal, from ingredient amounts to method and cooking time. This process includes triple-testing recipes to ensure they meet our high standards. The many stellar cooks and food editors who have been part of our team include Sarah Carey, Lucinda Scala Quinn, Jennifer Aaronson, Shira Bocar, Anna Kovel, Greg Lofts, Riley Wofford, Lauren Tyrell, and Lindsay Leopold. Editorial Guidelines Updated on June 12, 2017 Print Rate It Share Share Tweet Pin Email Prep Time: 25 mins Total Time: 50 mins Servings: 4 Even carnivores will give this hearty burger the thumbs up. Ingredients 4 large portobello mushrooms, stems removed 1 tablespoon olive oil Coarse salt and ground pepper 1 ripe avocado, pitted, peeled, roughly chopped 1 tablespoon spicy brown mustard 1 tablespoon horseradish 1 tablespoon fresh lime juice 1 jalapeno chile, finely chopped (ribs and seeds removed, for less heat), if desired 4 soft rolls, split horizontally 1 beefsteak tomato, cored and thinly sliced Directions Preheat oven to 425 degrees. On a large rimmed baking sheet, toss mushrooms with oil and 2/3 cup water; season with salt and pepper. Arrange stemmed side down; cover loosely with foil. Roast until tender, 30 to 45 minutes. Meanwhile, in a medium mixing bowl, mash avocado with a fork. Stir in mustard, horseradish, and lime juice. Fold in jalapeno season with salt and pepper. Toast rolls. Dividing evenly, layer each bottom half with tomato and portobello, and each top half with avocado mixture. Rate it Print