To make the sauce, add the tomatoes to a blender or food processor. Puree until smooth, adding a bit of the reserved liquid if necessary to smooth the mixture out. Melt the butter in a large, deep skillet or sauté pan over medium-high heat. Cook the onion just until it begins to soften, about 1 minute. Stir in the tomato paste, garlic and red pepper flakes and cook just until fragrant, about 30 seconds. Stir in the tomato mixture and reduce heat to a simmer. Cook for 5-8 minutes, until the sauce is slightly thickened. Season to taste with salt and pepper. Remove the pan from the heat and stir in the cream. Set aside.

To make the meatballs, combine the panko, grated onion, parsley, basil, Parmesan, salt, pepper, garlic and egg in a large bowl. Stir together with a fork just until blended. Mix in the ground chicken and knead together gently until evenly combined. Form the mixture into meatballs about 1½-inches in diameter.

Heat the oven to 400º. Heat the olive oil in a large skillet over medium-high heat. Add the meatballs to the pan in a single layer (you may need to do this in two batches). Cook, turning occasionally, until all sides are browned.

Once all of the meatballs are browned, transfer them to the pan with the tomato sauce. Sprinkle the mozzarella and additional Parmesan over the top. Bake until the cheese is fully melted and bubbling and the meatballs are cooked through, about 15 minutes. If you would like to brown the cheese a bit more, place the meatballs under the broiler for 2-3 minutes.

Remove from the oven and garnish with the fresh basil. Serve warm.