Preheat the oven to 200°c. Line two baking trays with parchment or foil. Top with a wire rack and spray with cooking spray.
Heat olive oil in a medium pan over medium-high heat. Toast the panko crumbs, stirring, until lightly golden brown, about 3 minutes.
Pat the chicken dry. Set up a 3-step breading station in three separate bowls or plates. In one, add the coconut flour. In another, combine the eggs with a pinch of salt and pepper. In the third, combine the toasted panko crumbs with the coconut, 1 teaspoon salt, and ½ teaspoon pepper.
Dip the chicken fillets into the coconut flour first, shaking off any excess, then into the eggs, and finally into the coconut panko mixture, pressing the mixture onto the chicken. Place on prepared baking trays. Spray with cooking spray and bake for 18-20 minutes or until cooked and golden brown.
While the fillets are cooking, make the dipping sauce. Puree the mango chunks and stir in the sweet chilli sauce.
Serve chicken fillets with the dipping sauce.