Trim any fat from the chicken breasts and dice into bite-size pieces about 3/4 inch square.
In a bowl, whisk together the buttermilk and hot sauce until combined.
In a shallow bowl, whisk together the flour, sea salt, black pepper, paprika, and onion powder.
Place the panko breadcrumbs in a third shallow bowl.
Heat the oil in a Dutch oven or heavy pot to 350°F (use a candy or deep-fry thermometer). The oil should be at least 4 inches deep; heating may take about 15 minutes.
Working in small batches, first coat chicken pieces in the seasoned flour, shaking off excess, then dip into the buttermilk mixture, and finally press into the panko to fully coat.
Carefully add a few coated chicken pieces to the hot oil, keeping the temperature at 350°F, and fry until deep golden brown and cooked through to 165°F in the center, about 2–3 minutes.
Use a slotted spoon to remove the chicken and drain on paper towels or brown paper bags to remove excess oil. Repeat with remaining chicken.
