Preheat the oven to 350 degrees. Dice the smoked mozzarella into 1/2-inch cubes. Set side.
In a food processor, pulse the shallots, sun-dried tomatoes, basil, shredded mozzarella, parmesan cheese, tomato paste, red pepper flakes, 1 1/2 teaspoon of salt and 1/2 teaspoon of pepper until blended. Transfer the mixture to a large bowl. Add the beef and pork and, using a wooden spoon or clean hands, stir until combined. Form into 1 1/4-to-1 1/2 inch meatballs. Insert 1 cube of smoked mozzarella into the center of each meatball and form meat around it, enclosing the cheese.
In a large heavy-bottomed saucepan, pour equal parts olive oil and vegetable oil to fill the pan halfway. Heat over medium-high heat until deep-fry thermometer reaches 350 degrees. In batches, fry the meatballs until dark brown, 1 to 2 minutes. Remove and drain on a paper towel-lined plate.
Place the fried meatballs on a foil-lined baking sheet. Put in the oven and bake until cooked through, 10 to 12 minutes. Cool slightly, then serve immediately with marinara sauce, if desired.