In a large bowl combine the ground chicken, 1 egg, dried oregano, mint, garlic powder, breadcrumbs, crumbled feta and salt. Mix very well and shape into meatballs. (I prefer using my hands for mixing and an ice cream scoop for shaping meatballs.) You should get approximately 24-25 meatballs.
Preheat the oven to 200C/400F.
Heat a tablespoon of olive oil in a large frying pan and brown the meatballs until golden on the outside but not cooked all the way through. You will need to do it in batches to avoid overcrowding. Then place the meatballs on a rimmed baking sheet and finish cooking in the oven for 8-10 minutes.
Alternatively you can skip browning and simply bake the meatballs for 15-20 minutes depending on the size or until the internal temperature reaches 74C/165F.
While the meatballs are in the oven, make the tzatziki dip. Grate the cucumber, then put in a clean cloth and squeeze out the liquid, discard the liquid. In a medium bowl combine the yogurt, grated or pressed garlic, lemon juice, grated cucumber, finely chopped fresh mint or dried mint and salt to taste. Combine and let sit for at least 10 minutes for the flavours to blend. Serve with the meatballs.