Set up an immersion circulator in a large pot and preheat the water bath to 155°F.
In a large bowl, whisk together buttermilk, eggs, hot sauce and chicken. And the chicken to a sealable bag before adding the buttermilk marinade to it. Massage the chicken so it is completely coated.
Use a vacuum sealer to vacuum seal the bag.
Sous Vide
Add sealed chicken to water bath and cook for 2 hours.
Deep Fry
In a shallow bowl, add flour, baking powder, paprika, salt, garlic powder and black pepper, mixing until combined.
Remove one piece of chicken from the bag. Allow some of the excess buttermilk to drip off before tossing in the flour mixture. Toss until every piece of chicken is coated, pressing your hands in it get the flour to adhere.
Fill cast iron skillet with oil about ¾" deep. Heat to 350°F. Working in batches, fry each piece of chicken about 3 minutes per side or until cooked through. Place chicken on a wire rack over a baking sheet and sprinkle with salt when done.
Notes
If you don't have a vacuum sealer, you can use a freezer grade zipper bag and zip almost to closed. Submerge the bag in the water and the air will start to come out and zip once everything is released.
Place some wet towels on top of the chicken so it remains submerged.
If you want spicier fried chicken, add 1 teaspoon cayenne pepper to the flour mixture.
Don't add too much chicken to the oil or you will lower the temperature so the skin won't get crispy. Cook in batches.
Use the oven at 200°F to keep the fried chicken warm while you are making everything in batches.