Fry onions with vegetable oil over low heat until golden. Remove to a large mixing bowl.
Add meat and all other ingredients except flour and olive/corn oil mix. Knead for about 10 minutes or until mixture is a smooth paste.
Heat the oil mix in a large frying pan to the point of fragrance.
Meanwhile, start to shape mixture into balls about the size of a large marble by rolling lightly between palms of hands, I suggest that you do them in batches of say 12 - 16, each batch being enough to space evenly but separately in the frying pan.
As each meatball is formed place them on a large plate which has been liberally covered with plain flour. When the batch is finished lightly roll the meatball in the flour. At this point the oil in the frying pan should be just ready.
Put the batch of meatball into the pan (Use kitchen tongs as the oil is very hot).
Start on your second batch of meatballs, make them and place them on the floured plate. At this point it is time to turn the meatballs over and when you have completed this roll the second batch in the flour.
Now it is time to remove the first batch from the frying pan using a slotted spoon or kitchen tongs and place on paper towels to drain.
Put the second batch of meatballs into the pan to cook and carry on with the process until you have finished the mixture.
Making the tsatziki: Peel the cucumber, cut it in half and use a teaspoon to scrape out the seeds.
Chop the cucumber finely.
Peel and press the garlic.
Mix the cucumber, garlic, mint, and yogurt, with salt and pepper. Make the tsatziki at least 2 hours ahead to give the flavors a change to develop.