Recipe: Slow Cooker Sweet and Sour Meatballs

Name: Recipe: Slow Cooker Sweet and Sour Meatballs
Ingredients: 1/4 cup cornstarch; 3 tablespoons water; 1 cup unsweetened pineapple juice; 1/2 cup rice vinegar; 2 tablespoons soy sauce or tamari; 1/4 cup ketchup; 1/4 cup packed light brown sugar; 1/2 large yellow onion, cut into 1-inch pieces; 1 large red or green bell pepper, cored, seeded, and cut into 1-inch pieces; 1 large egg; 1/2 cup panko breadcrumbs; 1/4 cup whole or 2% milk; 2 teaspoons kosher salt; 1 teaspoon ground ginger; 1/4 teaspoon freshly ground black pepper; 2 pounds lean ground beef; 1/2 large yellow onion, finely diced; 3 cloves garlic, minced; 2 medium scallions (green parts only), thinly sliced