For the sauce:
¼ cup fresh lemon juice
¼ cup canola oil
¼ cup yellow mustard
2 tablespoons hot sauce (or less to suit your taste)
2 tablespoons brown sugar
3 cloves garlic, crushed
1 fresh chili pepper, minced
½ cup canned pickled hot peppers, diced, plus 1/4 cup liquid from the can
For the chicken:
6 boneless, skinless chicken breasts (about 2 ½ pounds)
2 cups flour
½ cup cornstarch
1 teaspoon baking powder
4 egg whites
1 cup canola or peanut oil for frying
Whisk sauce ingredients together in large bowl. Set aside.
Butterfly each chicken breast by cutting through the thickness with a sharp knife to yield 2 thinner cutlets. Cut each crosswise into ½” strips to form “fingers.” Place them in a large zipper storage bag. Add 1/4 cup of the sauce to bag and gently squeeze bag to coat chicken with sauce. Marinate in the refrigerator for 30 minutes (or up to 2 hours).
In large bowl, combine flour, cornstarch, and baking powder. Add 6 tablespoons of the sauce and stir it together until the mixture resembles coarse, wet sand.
In another large bowl, whisk egg whites until frothy. Line a sheet pan or tray with parchment paper.
Remove chicken from marinade and pat dry with paper towels. Dip chicken, one strip at a time in egg whites and then into flour mixture, pressing lightly to adhere.
Heat oil in large skillet over medium-high heat until it has reached 345 degrees F or the surface is shimmering. Carefully place chicken strips in oil and fry until golden brown and cooked through, 3 to 4 minutes per side. Drain on paper towels. Repeat with remaining chicken strips. Transfer chicken to platter, drizzle with remaining sauce, and serve.