1. In a bowl, put the ground chicken and add in lemon juice, oregano, basil, olives, green onions, garlic, olive brine, feta cheese and black pepper. Using your hands, mix everything into the meat, making sure everything is mixed throughout the meat. Wrap with plastic wrap and place in the fridge for about 15 – 20 minutes.
2. Grill the mushrooms in a pan with just a little bit of olive oil (about a teaspoon if it’s a non stick pan) over medium heat.
3. Remove the meat from the fridge and make into 4 equal parts. Roll the meat into balls, then flatten with the palm of your hand. Place on a hot grill or in the oven set on broil. Cook the patties for about 10 minutes, flipped half way through. Cook until juices run clear.
4. Lightly toast buns on the grill.

Tzatziki Sauce

1. Using a cheese grater, grate the cucumber. Once grated, squeeze the extra liquid out of the cucumber and place in a bowl with the garlic.
2. Drain any excess liquid from the yogurt with the use of a cheese cloth.
3. Put the yogurt into the bowl with the cucumber and mix together, seasoning with the salt and pepper.
4. Put a bit of the tzatziki sauce on the bun and layer with lettuce, burger, tomato, pepperocinis and grilled mushrooms.