Whisk together the first 5 ingredients. Then toss 80% of this marinade with the potato chunks in a large bowl. Reserve the remaining 20% of the marinade.
For the onion and mint, chop in a food processor to get nice and small pieces - you can also chop with a knife.
In a large bowl, using your hands, combine the ground meats, eggs, onion, mint, garlic, breadcrumbs, 3 tbs olive oil, red wine vinegar, salt, cumin and chili pepper flakes. Next, form large meatballs and then shape them into sausage oblongs. Place them in a 9x13” baking dish spaced apart as best as possible. Then add the potatoes to the dish.
Now take the remaining marinade from before and drizzle it on the soutzoukakia tops.
Tightly cover the baking dish with aluminum foil and bake for 30 minutes.
After the 30 minutes, decrease the temperature of the oven to 425° F. After 15 minutes, remove the dish from the oven and uncover. Place back in the oven for 15 more minutes. If they are not yet golden brown, pop on your broiler and broil for a few minutes.