To prepare the polpettone ripieno recipe, first you need to make the sauce. Heat the olive oil in a large skillet over medium-high heat. Add the garlic and saute until fragrant, about 1 minute. Stir in the tomato paste and cook, scraping up any browned bits from the bottom of the skillet, until the mixture is thickened. Remove the pan from heat and add the salt and pepper to taste.