Place the chicken pieces in a bowl and pour 1/2 cup buttermilk over them; toss to coat and let sit while you prepare the coating.
Preheat the oven to 425°F (220°C) and line a baking sheet with parchment paper.
In a medium bowl combine the finely crushed corn flakes, paprika, and a pinch of kosher salt and black pepper; stir to mix evenly.
Working one piece at a time, lift the chicken from the buttermilk allowing excess to drip off, then press into the corn flake mixture to coat on all sides; place coated pieces on the prepared sheet without crowding (use a second sheet if needed).
Lightly brush or mist the coated chicken with olive oil, then bake the chicken until cooked through, about 15–20 minutes.
While the chicken bakes, make the honey BBQ sauce by whisking together 3/4 cup BBQ sauce, 1/4 cup honey, 2 tablespoons Dijon mustard, and 1/2 teaspoon cayenne in a jar or bowl until smooth.
Remove the chicken from the oven, drizzle or brush the honey BBQ sauce over each piece, then return to the oven for about 5 minutes to warm the sauce and finish glazing.
To make the spicy ranch, combine 1 cup plain Greek yogurt, 1/2 cup buttermilk, 1 tablespoon dried parsley, 2 teaspoons dried dill, 1 teaspoon garlic powder, 1 teaspoon onion powder, 1 teaspoon kosher salt, and the chopped jalapeño in a jar or bowl and stir or shake until creamy.
Garnish the glazed chicken with chopped fresh chives and serve immediately with the spicy ranch for dipping.