In a food processor, pulse the walnuts until finely chopped. Transfer to a mixing bowl and combine with breadcrumbs, garlic powder, salt, and pepper.
Brush each chicken breast with olive oil, then dip into the beaten egg. Coat each breast with the walnut mixture, pressing gently to adhere.
Place the coated chicken breasts on a baking sheet. Bake in the preheated oven for 25 minutes or until the chicken is cooked through and the crust is golden brown.
Let the chicken rest for a few minutes before serving. Enjoy!