In a resealable zip bag, combine together the flour, cornstarch, paprika, garlic powder, onion powder, salt, black pepper, mustard powder, and cayenne.
In a shallow bowl, whisk the egg and water together, set it aside.
Remove the tendon from the chicken tender: Grab ahold of the tendon with a paper towel. Slide the tendon through the tines of a fork and press down while pulling the tendon through the tines.
Pat the chicken tenders fully dry with paper towels.
Sprinkle the chicken with salt, pepper, garlic powder, and paprika. Set aside.
Pour about ¼ inch of oil into a large skillet. Heat over medium to medium-high heat until the oil reaches about 350°F.
While the oil is heating, dip each chicken tender into the egg wash, letting the excess drip off. Immediately place it into the bag of seasoned flour. Repeat with all the chicken pieces. Press the flour onto all sides of the chicken to get a good coating. (For an extra-crispy crust, dip the flour-coated chicken back into the egg wash and then into the flour a second time, you will want to use two eggs and double the ingredients for the flour mixture).
Once the oil is hot, carefully place 2-4 chicken tenders (depending on their size) in the pan, making sure not to overcrowd the skillet. Cook for about 3-4 minutes per side, or until golden brown and the chicken reaches 165° in the thickest part.
Transfer the chicken to a wire rack set over a paper towel lined baking sheet. Let it rest for a few minutes before serving.