Make the olive tapenade. Add Spanish and Castelvetrano olives, olive oil, lemon juice, capers, garlic, and red pepper flakes to a mini food processor. Pulse until finely chopped, scraping down the sides when necessary. Taste and add additional red pepper flakes if desired. You can keep it finely chopped or pulse further for more of a paste, if you want.
5 oz Spanish olives, 5 oz Castelvetrano olives, 1-2 tablespoons olive oil, 2 teaspoons lemon juice, 2 teaspoons capers, 1 clove garlic, 1/4 teaspoon red pepper flakes
Prepare the chicken burger patties. Add the ground chicken and 1/4 cup of olive tapenade into a medium bowl. Cut off ¼ of the block of feta and crumble into the bowl as well (about 1/2 cup crumbled, or 2 oz. by weight). Mix with a wooden spoon until evenly distributed. Depending on your specific chicken, the mixture may be sticky - you may add some breadcrumbs to soak up some moisture if desired, but don't worry if it's still sticky. It'll all work out when it cooks. Just use parchment paper to hold the patties in the meantime.Divide burger mixture into four equal parts and shape into burger patties slightly larger than the buns to allow for shrinkage during cooking. Use parchment paper between patties to keep them from sticking to each other.
1.5 lbs ground chicken, 8 oz. feta cheese, ½ cup green olive tapenade
Toast the buns. Preheat a skillet (I used cast iron) over medium heat. Butter the buns and toast them cut side down in the skillet until golden brown. Set the buns aside.
Cook the burgers. Add 1 tablespoon of butter to the preheated pan and cook the chicken feta burgers for 5 minutes per side, or until internal temperature reaches 165℉. You can just the parchment paper to transfer the uncooked patties to the pan, and peel it off after placing the patty in the pan (see video if necessary).Slice remaining feta cheese into thin slices and add two slices to each burger in the last couple minutes of cooking. Cover the pan with a lid to help the cheese melt. Remove the burgers to a plate.
5 tablespoons butter, 8 oz. feta cheese
Sauté the spinach. Drizzle pan with 1 tablespoon of olive oil and add spinach and a pinch of salt. Sauté until just wilted but still bright green, about 1-2 minutes.
5 oz. spinach, 1 tablespoon olive oil, kosher salt
Assemble the burgers. Spread each bottom bun with 1 tablespoon of olive tapenade and each top bun with mayo. Add chicken burger with feta cheese to each bun and divide the spinach between the burgers.
mayonnaise
Enjoy! Serve burgers with cucumber tomato salad, Greek pasta salad, or your favorite sandwich side.