How to Make It
Marinate the chicken: In a large bowl, combine the buttermilk, mustard powder, paprika, lemon zest and Tabasco; season with salt and pepper. Submerge the chicken in the marinade, cover and refrigerate for 12 to 24 hours.
Meanwhile, make the pretzel crust: In a medium bowl, combine the pretzel crumbs, sourdough pretzels, mustard powder, paprika, onion and garlic powders and season with salt and pepper.
Make the mustard sauce: In a medium bowl, mix the Dijon with the vinegar, honey, whole-grain mustard. Stir in the canola oil until combined.
Batter and fry the chicken: Place a wire rack on a large rimmed baking sheet. In a large bowl, mix the flour, cornstarch, baking powder and soda water until combined. Remove the chicken from the marinade and season with salt and pepper. Coat the chicken in the batter, then dredge in the sourdough pretzel mix, shaking off any excess. Transfer to the wire rack.
In a large Dutch-oven or cast-iron skillet, heat 1 inch of vegetable oil to 350°. Working in small batches, gently place the chicken in the hot oil and fry on both sides until golden brown and crisp, about 10-15 minutes, until a thermometer inserted in the thickest part of a breast or thigh reaches 160°. Serve immediately with mustard sauce.