Souvlaki

One at a time, place the chicken breasts in a 1-gallon zip-lock bag; using a meat mallet, pound to an even ½-in (13-mm) thickness. (Skip this step if using chicken tenderloins.) Cut the meat into 2-in (5-cm) chunks.

Mix all the ingredients except for the chicken together in a large bowl. Add the chicken pieces to the bowl and stir until evenly coated. Cover with plastic wrap and let the chicken marinate in the refrigerator for at least 4 hours or overnight.

Thread the marinated chicken onto skewers, folding if the pieces are long and thin. Be sure not to cram the skewers (see note).

Preheat the grill to medium-high heat and, using tongs, dip a wad of paper towels in vegetable oil and carefully wipe the grill grate several times to prevent sticking. Place the skewers on the grill and cook, covered, turning to brown evenly, until the chicken is cooked through, 5 to 7 minutes total. Transfer the chicken to a platter and cover to keep warm. Meanwhile, briefly grill the pita bread until warmed through. Serve with tzatziki sauce, warm pita, and lemon wedges.

Combine all of the ingredients in a medium bowl and mix until well combined. Taste and adjust seasoning if necessary. Cover and chill for up to 2 days or until ready to serve.