Prepare the Meatball Mixture: In a large mixing bowl, beat one large egg and stir in chopped fresh parsley, tomato paste, dried oregano, salt, black pepper, minced garlic, and water until well combined. Add ground beef and ground pork, followed by Italian bread crumbs. Mix thoroughly until all ingredients are incorporated, then form the mixture into golf ball-sized meatballs.

Bake the Meatballs: Preheat your oven to 350°F (175°C). Place the formed meatballs on a lined baking sheet, ensuring they are evenly spaced. Bake for 20 minutes, flipping the meatballs halfway through to ensure even cooking and a nice golden-brown crust.

Sauté the Onion and Garlic: In a large skillet, melt butter over medium heat until it sizzles. Add a chopped yellow onion, stirring occasionally for about 5 minutes until softened and translucent. Incorporate the remaining minced garlic and sauté for an additional minute until fragrant.

Create the Creamy Marinara Sauce: Pour in the marinara sauce and add a pinch of sugar to balance acidity. Stir well, allowing the sauce to come to a gentle simmer. Reduce the heat to low and mix in heavy cream, stirring continuously until the sauce thickens slightly and is beautifully creamy.

Cook the Spaghetti: Bring a large pot of salted water to boil. Add spaghetti and cook according to package instructions until al dente, usually around 8-10 minutes. Reserve some pasta water, drain the spaghetti, and return it to the pot.

Combine and Serve: Gently fold the baked meatballs into the creamy marinara sauce. Add the cooked spaghetti to the skillet, tossing everything together to ensure the pasta is evenly coated in the sauce.