If using milk and lemon juice instead of buttermilk, prepare that first. Mix together the milk and lemon juice and let it sit for at leave 5 minutes to let it thicken and curdle slightly to resemble buttermilk. Set aside.
Prepare the chicken – If using breasts, filet them in half (or thirds for larger breasts) and cut in half to make short thin pieces. If using thighs, remove most of the fat. Add the chicken to a bowl and add all the marinade seasonings. Top it with the buttermilk (or milk and lemon juice mixture), mix well to make sure the chicken is fully covered with the milk and seasonings. The marinade should be a light pink color from the spices. Set aside – this can sit in the fridge for 3-4 hours or overnight.
When you’re ready to make the chicken, add your oil to a skillet and heat to medium high. Prepare the flour mixture by combining all the breading ingredients on a plate. Spoon in about 2 teaspoons of the liquid marinade into the flour mixture until some pebble size pieces of flour are mixed in throughout the breading. Remove the chicken from the marinade one piece at a time and let the excess liquid drip off. Add it into the breading and coat each side generously. Once the oil is heated through, add the chicken into the skillet in batches and cook flipping once until golden brown on each side and the inside temperature reaches 165F. Remove the chicken and set on a cooling rack.
While the chicken cooks, prepare the Greek yogurt ranch/blue cheese dressing by combining all ingredients together. Add the buffalo sauce and butter to a small skillet and warm through on low heat over the stove or in a bowl in the microwave. Prepare all desired toppings for your crispy buffalo chicken sandwich. Set aside. Toast up the burger buns in a nonstick skillet with a touch of butter to develop a golden color on the inside of each half.
Assemble your sandwiches by adding some Greek yogurt dressing on the bottom bun. Dunk each piece of chicken in the buffalo sauce and add it right on top of the yogurt dressing. Top with tomatoes, lettuce and pickles or other toppings of choice, add a small amount of dressing to the top bun and place it on top. Dig in! Enjoy!