In a pan over medium heat, add a drizzle of olive oil. Add the onions and a pinch of salt. Cook for 1 to 2 minutes, then reduce the heat to low and cover. Cook for 10 to 15 minutes, stirring occasionally, until softened and golden.
Add the white balsamic vinegar and continue cooking for 5 minutes, until the onions are well caramelized. Let cool slightly.
In a small bowl, tear the bread into pieces and pour the milk over it. Let soak for a few minutes.
In a large bowl, combine the ground beef, caramelized onions, soaked bread, egg, oregano, and Parmesan cheese. Drizzle with basil olive oil. Season generously with salt and pepper.
Form into about a dozen meatballs.
Skillet option: Brown the meatballs in a large skillet over medium heat with a little olive oil, about 8 to 10 minutes, turning them regularly. Set aside.
Oven option: Bake at 220°C (425°F) for about 15 to 20 minutes, until golden brown. Set aside.
In a skillet, add a drizzle of olive oil. Sauté the garlic pieces over low heat for 1 to 2 minutes, being careful not to burn them.
Add the passata and a few basil leaves. Season with salt and pepper and simmer for 4 to 5 minutes.
Place the meatballs in the passata. Cover and simmer over low heat for about 10-12 minutes to coat and tenderize.
Garnish with grated Parmesan cheese and a drizzle of basil-infused olive oil. Serve hot with crusty bread or pasta.
