Preheat water bath using immersion circulator to 155 degrees F.
Spatchcock your chicken by removing the back bone with very sharp kitchen shears or a pairing knife. Remove the neck, loose skin, and any organs and discard or save for stock. Pat the chicken dry thoroughly with paper towels.
In a small bowl, mix together the butter, kosher salt, garlic powder, and Italian seasoning.
Rub the chicken all over with the butter mixture. Add to a vacuum seal bag and vacuum seal.
Add the chicken to the water bath and cook for 6 hours.
When it's done cooking, you can refrigerate to serve later or prepare it to serve immediately.
To finish, preheat your oven to 450 degrees F. Line a baking sheet with foil. Place the chicken on the lined baking sheet and cook for 15-20 minutes in preheated oven until skin is crispy and golden and chicken is heated through.