Choose boneless, skinless chicken breasts. This recipe is for about 2 large breasts but can be increased.
Trim breasts of excess fat. Place them, one at a time in a large heavy-duty ziplock bag, and gently pound to about an even thickness.
Remove the breasts to a cutting board, and cut into evenly sized pieces - you will probably get 8 pieces from each one.
Marinade
Combine the buttermilk, salt, garlic powder, and paprika in a flat dish, like a pie plate. Use a fork to beat the ingredients together. Add the chicken, in an even layer. Turn each piece to get them well coated.
Try to marinate for a minimum of 10 minutes, but several hours or overnight is even better. More marinating means more tender chicken.
Make the breading
Using another shallow dish, combine the bread crumbs, cornmeal, and all of the remaining spices - stir with a fork until blended evenly.
Bread the chicken
If you plan to cook these right away, preheat the oven to 400°. Line a heavy baking sheet with parchment paper for easy cleanup. Place a cooling rack [see equipment, above] on the sheet pan. It is better to wait an hour or so at least. It also gets the prep out of the way ahead of time.
If waiting until later to cook, you still want to line a heavy baking sheet with parchment paper, and a rack of some kind to keep the chicken up off the paper. I use a cooling rack. This ensures crispier chicken.
Take each piece of the chicken from the marinade, shake to remove excess marinade, and dip all sides in the breading mixture. Make sure to get every surface coated in the crumbs.
Lay the chicken in an even layer on the rack that is sitting on the sheet pan. If you find spots with no breading, you can dip them back into the breading mixture. Discard any remaining marinade and breading mixture - they both have chicken juice in them at this point, so they aren't safe to use another time.
You can safely leave the tenders at room temperature for up to an hour at this point. If you want to let them sit any longer than that, they need to go in the fridge.
Oven frying the chicken
Preheat the oven to 400°. Carefully, pick up the cooling rack and set it to the side. Spray each tender with the avocado oil spray, trying to get a light, but even amount on each one. Place them, oil side down on the parchment-lined baking sheet. [you can shake the parchment over the garbage or sink to get excess crumbs off first.]
Spray the second side of each piece with avocado oil spray. Place in the preheated oven for 9 minutes, turn over, and place back in the oven for another 9 minutes. You can check for doneness with an instant-read thermometer. The internal temp in the thickest part should be no less than 165°.
Remove from the oven and serve right away, with guacamole, sour cream and salsa, or whatever topping you prefer.
Notes
*Chipotle hot sauce and chili powder can be quite spicy, so consider the tolerance of hot flavors of the people you're serving. You can leave it out of the marinade, or sub in something not quite so spicy, like regular chili powder. You can even leave the spicy stuff out entirely if you like - these are still delicious, even without a lot of heat.