In a large mixing bowl, add ground beef, pork, salt, pepper, brown sugar, and soy sauce. Set aside.
Clean outer leaves of the lemongrass if showing signs of discoloration. Trim the top and the very bottom base of the stalk leaving the small bulb about 4 inches long and 1 in wide. Discard the top and discolored bottoms. Split the base of the remaining stalk down the center, using a chefs knife, chop the lemongrass stalk roughly. You will need about 1 cup chopped. Transfer to food processor and process on high until lemongrass resembles a fine mince.
Add shallots, garlic to the lemongrass mixture in the food processor. Process 10-15 seconds until finely chopped. Remove from food processor and transfer mixture to the ground beef and pork mixture. Combine thoroughly until both meats are blended uniformly. Using a 3oz scoop, dish out 4 meatballs, press gently into thick patties and place on tray. Cover and refrigerate until ready to cook.