In a wide bowl, whisk the buttermilk with a pinch of salt. Add the chicken pieces and toss to coat. Let them marinate for 10 to 15 minutes to tenderize the meat and infuse flavor.
While the chicken rests, set up your breading station: in one shallow dish, combine flour, cornstarch, paprika, garlic powder, onion powder, salt, and pepper. In another dish, you can place a light splash of oil or keep it dry if you prefer a crisper finish.
Dredge each marinated chicken piece in the seasoned flour mixture, pressing gently so the coating adheres well. Place the coated nuggets on a rack or parchment-lined tray as you finish the batch.
Heat about 1 inch of oil in a heavy skillet or Dutch oven to 350°F (175°C). If you don’t have a thermometer, test with a small piece of coating—it should sizzle and rise to the top reasonably quickly.
Fry the chicken in batches, being careful not to crowd the pan. Cook for about 3 to 4 minutes per batch, turning once, until the coating is deeply golden and the chicken is cooked through (internal temp should reach 165°F / 74°C). Transfer to a wire rack or paper towels to drain excess oil.
While the first batches fry, whisk together the honey, mustard, and mayonnaise in a small bowl to create a glossy, tangy dipping sauce. Taste and adjust with a touch more honey or mustard if you prefer it sweeter or sharper.
Serve the popcorn chicken hot with a generous pool of honey mustard on the side or drizzle lightly over the top. For an extra touch, you can add a sprinkle of flaky salt or sesame seeds.
If you want a healthier angle, you can finish the chicken in the oven after frying by placing the fried nuggets on a lined baking sheet and baking at 400°F (200°C) for 6 to 8 minutes to set the crust a bit more without soaking up extra oil.