In a large bowl, combine the ground beef, eggs, breadcrumbs, finely diced onion, salt, black pepper, garlic powder, and Worcestershire sauce. Mix gently with your hands until just combined—overworking the mixture will make the meatballs tough and dense. Form the mixture into approximately 40-45 one-inch balls and arrange them on a foil-lined baking sheet sprayed with cooking spray. I find that slightly wetting my hands helps prevent sticking and creates more uniform, compact meatballs.

Heat the broiler to high and place the baking sheet on the middle rack. Broil for 8-10 minutes, until the meatballs are cooked through (they should reach an internal temperature of 160°F). You're not looking for deep browning here—just cooking them through so they hold their shape when transferred to the slow cooker.

While the meatballs are broiling, combine the chili sauce and grape jelly in a saucepan over medium-low heat. Stir frequently until the jelly is completely melted and the sauce is smooth and well combined, about 3-4 minutes. The jelly will thin out slightly as it melts—this is exactly what you want for a glossy, coating sauce. I like to taste the sauce at this point and adjust the sweetness or tang if needed, though it's usually perfect as is.

Spray the inside of a slow cooker with cooking spray. Transfer the broiled meatballs from Step 2 to the slow cooker, then pour the sweet and sour sauce from Step 3 over them. Gently toss to coat all the meatballs evenly with the sauce. Cover and cook on low for 3 hours—this allows the flavors to meld and the sauce to thicken slightly while keeping the meatballs moist and tender.

After 3 hours, the meatballs will be tender and glazed with the sauce. Transfer to a serving bowl or platter and sprinkle with freshly chopped parsley for color and a fresh herbal note that balances the sweet and savory flavors. Serve warm, either on toothpicks as an appetizer or over rice as a main dish.