This Slow Cooker Sizzling Mongolian Beef is a delicious and easy-to-make dish that is perfect for busy weeknights. Tender strips of beef are slow-cooked in a flavorful sauce made with soy sauce, brown sugar, garlic, ginger, and red pepper flakes. The beef becomes incredibly tender and flavorful, and the sauce thickens to a rich and sticky glaze. Serve this Mongolian beef over steamed rice and garnish with green onions for a complete and satisfying meal.