I find these burgers need no additional condiments. Recipe can be doubled, and burgers can be frozen for a week or so. If you can, allow these burgers to sit in the fridge for up to 8 hours for the flavours to really come together.
My Grandmother (Teta) made this dish as an accompaniment to Chicken, Pork, or Lamb dishes. My son will make a meal out of it on its own. The yogurt and pine nuts really enhance the flavour, but are optional. To truly enjoy this I would not recommend using ground beef. It also very easily reheats and can be frozen as well.
These meatballs are very different because of the texture created after mixing in the food processor. I usually use a homemade tomato sauce but a good store bought sauce will work fine as well (Tomato & Basil). Top meatballs with sauce and mozzarella cheese and let your taste buds delight. Even Nona says she loves them.
For best results prepare this one-day ahead. When the ingredients are allowed to blend overnight the flavour is amazing. An incredible soup that can be a meal on its own. Be prepared; all the chopping takes time if you are doing it by hand. I cheat by running the vegetables through the food processor twice.