In a large casserole dish, pour the buttermilk and season with sea salt and black pepper. Place the chicken in the buttermilk and mix until evenly coated. Cover and place in the fridge for 1 to 2 hours or overnight.
Preheat oven to 180 C / 365 F and arrange a baking tray in the middle shelf.
Place cornflakes, panko, olive oil, spices (if using) in a food processor, and season with sea salt and black pepper to taste. Mix until finely crumbled and place in a large bowl.
Shake off the excess buttermilk from the chicken, then dip each piece in the cornflakes mixture and coat evenly, patting with fingers to make the crumbs stick.
Cover the hot baking tray with parchment paper, spray with a little olive oil and arrange the chicken tenders over it.
Bake for 20 minutes, or until the chicken internal temperature reaches 73°C / 165°F.
Take the chicken out of the oven and serve immediately with your favorite dips.