Preparing the Chicken: Slice the chicken in half lengthwise. Place in a resealable bag, or cover with plastic wrap, and using a meal mallet or rolling pin, pound the chicken out to 1/4” thickness. Repeat util you have 4 pounded out pieces of chicken breast. (Optionally, you can trim the chicken breast for smaller pieces). Place the chicken in an airtight container or resealable bag, and cover with buttermilk so that all chicken is fully coated/submerged. Marinate in the refrigerator for a minimum of 4 hours, or up to overnight. Once chicken in marinated, combine breading ingredients in a large bowl with a whisk until homogenous. Add a few tbsp of the buttermilk to the dry mixture and toss with a fork to form craggly pieces. Carefully remove each piece of chicken from the buttermilk, and coat evenly in the breading mixture. Transfer breaded chicken to a plate as you bread. Once all chicken is breaded, allow to sit for at least 15 minutes, or refrigerate breaded chicken for up to 2 hours. Once ready to fry, add 2-3 inches of oil to a large cast iron skillet, and heat over medium-high heat. Heat oil for 5-7 minutes. To test oil, add a small pinch of the breeding to the oil. If it disintegrates immediately, the oil is ready. Working in batches of 2 at a time, add the chicken to the hot oil, dropping away from yourself. Fry for 3-4 minutes a side, until golden brown and crispy. Once chicken is cooked, transfer to a wire rack set over a baking sheet to drain. Repeat until, all chicken is fried. Melt butter on the stove or in a microwave safe bowl, and whisk together with hot sauce. Transfer to a vessel large enough to coat the chicken in, such as a wide deep bowl or baking dish. Carefully dip each side of the chicken to coat, and set on the wire rack until ready to assemble the sandwiches. Making the Dilly Blue Cheese Sauce: Finely chop the dill. Add all ingredients to a bowl, and stir well to combine. Sauce can be made up to 2 days ahead. Assembling the sandwiches: Toast the buns cut side down in melted butter in a pan until golden. Add a layer of spring mix on the bottom of each bun. Top spring mix with sauced chicken, then with a dollop of the dilly blue cheese and the top bun.