Preheat oven to 400 degrees Fahrenheit.
Add parchment paper to a large rimmed baking sheet. Set aside.
Whisk together the egg and the buttermilk in a large, shallow bowl. Set aside.
Add the panko bread crumbs to a large shallow bowl and combine with the remaining ingredients: Italian seasoning mix, dried basil, garlic powder, paprika, red pepper flakes, salt and pepper. Stir to combine.
Pat dry the fish filets, using tongs or by hand, take a fish filet, dip it into the buttermilk mixture, toss into the breadcrumb mix. Place on the prepared baking sheet. Repeat with the others.
Ensure the breadcrumb mixture is not soggy or wet after tossing the first filets, if needed add more panko breadcrumbs. For a thicker coating, after the first round of dipping, dip each fish filet again into the buttermilk mixture and breadcrumb mixture. In that case the panko breadcrumb quantity should be doubled.
Bake for 12-15 minutes or until the coating is golden brown and fish is fork tender. Spray with cooking spray mid baking for the coating to have a shiny, golden brown color.
Remove from oven, lightly squeeze some lemon juice onto the fish filets and garnish with parsley. Serve with lemon aioli and lemon wedges on the side.