For the meatballs: In a mixing bowl, add the tuna, egg, bread crumbs, raisins, pine nuts, Parmigiano cheese, and 1/2 cup wine. Combine the ingredients together using your hands. To absorb any excess moisture, add flour. Wet your hands and make compact little balls with the mixture. Repeat with the remaining mixture. Dip the uncooked tuna balls in the sesame seeds.
Heat up extra-virgin olive oil in a saucepan. Gently place the meatballs in the hot oil and fry until golden brown. Turn the balls over to cook on all sides. Transfer to a plate lined with an absorbent paper towel.
For the balsamic sauce: Add the balsamic vinegar to a saucepan and cook on high heat. Add the rosemary and bring to a boil. Lower the heat to minimum. Let the balsamic reduce to half or when the sauce resembles a thick consistency. Drizzle the balsamic sauce over the meatballs.