Creating these Sweet & Sour Meatballs is simple. Follow these easy steps to achieve a mouthwatering dish:

1. Preheat Oven: Preheat your oven to 375°F (190°C). Prepare a baking sheet by lining it with parchment paper.
2. Mix Ingredients: In a large bowl, combine the ground beef, breadcrumbs, Parmesan cheese, chopped onion, minced garlic, egg, salt, and black pepper. Mix until well combined.
3. Form Meatballs: Shape the mixture into meatballs, about 1 inch in diameter. Place them on the prepared baking sheet.
4. Bake Meatballs: Bake the meatballs in the preheated oven for 20-25 minutes or until they are browned and cooked through.
5. Prepare Sauce: While the meatballs are baking, make the sweet and sour sauce. In a saucepan, combine ketchup, brown sugar, apple cider vinegar, soy sauce, Worcestershire sauce, and crushed red pepper flakes. Stir well and bring to a simmer over medium heat.
6. Combine Meatballs and Sauce: Once the meatballs are cooked, add them to the saucepan with the sweet and sour sauce. Stir to coat the meatballs evenly.
7. Simmer: Allow the meatballs to simmer in the sauce for an additional 5-10 minutes, allowing the flavors to meld.
8. Garnish: Remove from heat and sprinkle with fresh parsley if desired.

These steps will guide you in creating these incredible Sweet & Sour Meatballs with ease.