Very easy dish to make, can be made day ahead and placed in a crockpot to stay warm during a party or served at room temperature. So tasty, these won't last long on the party table. Recipe will make approx 32 1" meatballs or 40+ 3/4" meatballs.
Preheat oven to 350 degrees. Mix beef, onion, basil leaves, soy sauce, vinegar, beaten egg, salt & pepper in medium size mixing bowl. Form meatballs with 1 tbsp size scoops and place on lightly oiled sheeetpan. Bake about 20 minutes. Spoon meatballs into serving bowl and allow to sit for 10 minutes before serving.
Plum Sauce: Place preserves, soy sauce, hot sauce, rice vinegar, and brown sugar into small saucepan over medium-low heat. Stir the contents often to help the brown sugar to dissolve and the preservatives to liquify. Allow sauce to go just to a soft boil, lower heat, and continue heating for about 10 minutes so it reduces slightly. Remove from heat and allow to cool at least 10 minutes.
When sauce has slightly cooled, pour 1/2 of the sauce over the meatballs and gently mix well. Add more sauce if needed or reserve for future use.