Preheat oven to 400ºF.
Set up 2 dishes: one with the mustard and the other with the breadcrumbs and herbs.
Season the chicken breasts with salt and pepper, and run each first through the mustard and then through the breadcrumbs, to coat. Arrange chicken pieces on a cooling rack set on top of a baking sheet. Spray the chicken lightly with the cooking spray and bake until golden brown, crispy and cooked through, about 30 minutes. Serve.