Neapolitan Polpetta Burgers

Chef Jeff Starr suggested that you take a favorite recipe you already have in your repertoire and turn it into a burger, what a great idea! So I took our family's favorite Neapolitan Polpetta Sandwiches and turned them into burgers. I found that they were easier to eat than in the traditional meatball sandwich form and my family loved them! This recipe will work with any meatball recipe.
Ingredients
This recipe makes 8 large or 10 small : 
1 pound ground pork
1 pound ground beef
1 small clove garlic minced
1 pinch red pepper flakes
1/4 cup grated Parmigiano-Reggiano
1/4 cup Italian bread crumbs
1 egg
2 tablespoons chopped parsley
1/4 cup golden or regular raisins soaked in some warm wine or water and drained
1/4 cup pine nuts
1 tablespoon fennel seeds
*a little milk if it's too dry
*You will need a plate of flour to coat the burgers before frying
*You will  need a large pan and olive oil for frying
Toppings:
1 cup shredded Mozzarella cheese
4 cups Spaghetti Sauce
8 Whole Basil Leaves
Rolls:
You will need 8 round Italian Hoagie Buns (I remove some of the bread from the middle so the burger can fit and still close.)
Directions
Toast the pine-nuts and fennel seeds in a dry large pan (Use the same one you will be frying the burgers in) until the nuts are golden but not brown. Watch closely as the nuts can burn quickly!
Now slightly crush/cut this mixture along with the drained raisins with  a large chef knife, a food chopper or a mortar and pestle.
Mix the meat with all of the burger ingredients until well combined. If it is too dry add a little milk. Cover and place in fridge for an hour or more to allow the flavors to meld.
Form into 8 patties leaving a slight indention the middle of each one. Dip in the flour just to barely coat shaking off excess.
Heat up the pan on medium/high heat and then cover the bottom in olive oil.
Fry on each side just until golden, 2 minutes each side, add the sauce and cook for several minutes on medium/low heat. After 5 minutes check for an internal temperature reading of 140, this is enough for the pork to be safe but still moist.
Turn the oven broiler on and put a rack a few inches from the heating element. Remove the burgers and set aside.

Place the sauce from the pan on both sides of the buns.
Place each burger on one bun half (I use a large sheet pan to fit all the buns) and put some more sauce and then some cheese on both buns. Place in a oven under the broiler just until the cheese melts.Remove and place a basil leaf on each burger.