Crockpot Pepper Steak

Name: Crockpot Pepper Steak
Prep time: 10 min
Total time: 10 min
Cuisine: Asian
Ingredients: 1 1/2 lb. flank steak, cut into strips; Kosher salt; Freshly ground black pepper; 1 large red bell pepper, sliced; 1 large green bell pepper, sliced; 1 medium white onion, sliced; 2 inch piece of garlic, quartered; 2 garlic cloves, peeled and smashed; 1 c. low-sodium beef stock; 1/3 c. low-sodium soy sauce; 1/4 c. brown sugar; 3 tbsp. rice wine vinegar; 3 tbsp. sesame oil; 2 tbsp. cornstarch (optional); Cooked rice, for serving; Sliced scallion, for garnish; White sesame seeds, for granish