Food & Cooking Recipes Appetizers Mushroom-Polenta Diamonds Be the first to rate & review! 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 May 16, 2017 Print Rate It Share Share Tweet Pin Email Yield: 5 dozen The roasted red peppers give this savory bite some smoky sweetness and a touch of color. Ingredients 6 ounces shiitake mushrooms, stems removed, and caps wiped clean 1 tablespoon unsalted butter, plus more for baking sheet 1 small onion, minced 2 tablespoons port or dry white wine 6 tablespoons heavy cream 1 teaspoon coarse salt, plus more for seasoning Freshly ground pepper 1 cup instant polenta ½ cup freshly grated Parmesan cheese (2 ounces) 2 roasted red bell peppers, cut into thin slivers, for garnish (optional) Mascarpone cheese, for garnish (optional) Directions In a food processor, pulse mushrooms until finely chopped. Melt butter in a medium skillet over medium heat. Add onion; cook, stirring occasionally, until softened, about 4 minutes. Add mushrooms; cook until softened, about 3 minutes. Add port, and stir until evaporated. Stir in cream; simmer until mixture is thick, about 3 minutes. Season with salt and pepper. Remove from heat; let cool. Butter a 10-by-15-inch rimmed baking sheet; set aside. Boil 1 quart water in a large saucepan; add 1 teaspoon salt. While whisking constantly, gradually add polenta. Reduce heat to a simmer; cook, whisking constantly, until soft and all water is absorbed, about 5 minutes. Stir in Parmesan. Immediately transfer to prepared baking sheet; spread evenly. Let cool completely; cover with plastic wrap, and refrigerate until ready to proceed. Polenta can be made up to 1 day ahead. Halve the polenta crosswise. Carefully transfer one half, smooth side down, to a clean work surface; spread mushroom mixture on top. Place remaining polenta half, smooth side up, on top; trim edges. Cut polenta lengthwise into 3/4-inch-wide rows; cut rows at an angle to form 1-inch-long diamonds. Place on parchment-lined baking sheets. Wrap in plastic wrap; freeze until ready to use, up to 6 weeks. To serve, preheat oven to 425 degrees. Transfer sheets to oven. Bake diamonds, rotating sheets halfway through, 12 to 15 minutes. Garnish each with bell pepper and a dab of mascarpone, if desired. Serve warm. Cook's Notes To roast peppers, char them over a gas burner or under the broiler, turning them as they blacken. Place in a bowl; cover with plastic wrap. Let sit 15 minutes. Remove skins, seeds, and ribs. Rate it Print