Step 1

Place fry basket in air fryer, and preheat to 400°F for 10 minutes. Whisk together buttermilk and mustard in a shallow dish. Add chicken breasts to buttermilk mixture, turning to coat.

Step 2

Heat a small skillet over medium-high. Add panko to skillet; cook, stirring often, until golden brown, about 3 minutes. Let cool 10 minutes. Stir together panko, pecans, cheese, rosemary, salt, and pepper in a shallow dish.

Step 3

Dredge chicken breast in panko mixture. Coat preheated fry basket with cooking spray. Arrange 2 chicken breasts in basket, making sure chicken pieces are not touching. Coat chicken breasts with cooking spray. Cook 8 minutes. Turn chicken breasts over, and coat with cooking spray. Cook until a thermometer inserted into thickest portion of breast registers 165°F, 6 to 8 more minutes. Remove chicken breasts to a plate, and cover with aluminum foil to keep warm. Repeat procedure with remaining chicken breasts. Serve immediately.