Slow Cooker Mongolian Ground Beef Chow Mein

Name: Slow Cooker Mongolian Ground Beef Chow Mein
Ingredients: 1 1/2 pounds ground beef; 3 cloves garlic (minced); 4 tablespoons soy sauce; 2 tablespoons hoisin sauce; 1 tablespoon sesame oil; 1 tablespoon fresh ginger (grated); 1/2 teaspoon black pepper; 1/4 teaspoon red pepper flakes (optional); 1/4 cup brown sugar; 1/2 cup beef broth; 1 large onion (thinly sliced); 1 bag coleslaw mix (14 oz, undressed); 8 oz chow mein noodles (cooked according to package instructions); sesame seeds (for garnish); green onions (sliced, for garnish)