Place the chicken, garlic, shallots, egg, peanuts, Parmesan, and parsley in a mixing bowl. Sprinkle with 1/2 teaspoon salt and 1/4 teaspoon pepper. With your hands, combine the mixture until well blended.
Using a scoop or tablespoon, form the mixture into balls and place on a waxed paper-lined platter. Cover with foil and refrigerate at least 4 hours or overnight.
Place the oil in a large skillet over medium-high heat. Add the meatballs and brown all over for a total of 10 minutes.
Meanwhile, place the cream, Gorgonzola, and tomatoes in a saucepan over medium heat. Gently warm until the cheese is melted, stirring occasionally. Stir in the remaining salt and pepper and basil, if using.
Serve the meatballs with the sauce on the side for dipping, or place the meatballs in a serving bowl and ladle the sauce over the top.