This is my version of the gyro sauce, tzatziki. It's a sauce my mother-in-law taught me to make by taste and texture without any measurements. I've made faux gyros for years using pitas, thinly sliced roast beef, shredded lettuce and this sauce. Since we went vegetarian, I've REALLY been missing my gyros! This is as close to that as I can get and still be vegetarian! It was fantastic!
In a mixing bowl, whisk Miracle whip and vinegar together to desired consistency. Add sugar; whisk. Place prepared cucumbers and diced onion in large bowl; salt and pepper to taste. Pour Miracle Whip sauce over cucumber mixture; stir well. Refrigerate for minimum of 1 hour (sauce gets better the longer in fridge.)
Saute mushrooms and onions if desired. Set aside.
Cook frozen Boca veggie burgers on grill or in frying pan until heated to 160 degrees F. Season with Greek seasoning. At same time, butter and grill ciabatta rolls until golden and crisp.
Assemble burger, sauteed mushrooms & onions & tomatoes (if desired), shredded lettuce, and cucumbers dressing and cucumbers drizzled over top.