Preheat your oven to 400 degrees. This initial step is crucial as a hot oven will help achieve that desired crispiness right from the start.
In a medium mixing bowl, combine the panko or whole wheat bread crumbs, flour, salt, black pepper, and baking powder. Stir them together until evenly mixed, ensuring a uniform seasoning for each ring.
Now, take your large, thinly sliced onions and separate them into individual rings. This is where the magic begins—each ring will soon be coated and transformed!
Add the separated onion rings to the flour mixture, gently tossing to make sure all rings are coated. Be careful not to break the rings during this process.
Once coated, remove the onions from the mixture and set them aside. This step ensures that the flour mixture is not too wet when you dip the onions later.
In another bowl, whisk together the low-fat milk and egg white. This batter will add a light, crispy coating to the onion rings.
Add this milk-egg mixture to the leftover flour mixture and stir to combine, ensuring the batter is smooth and ready for dipping.
Dip each onion ring into the batter, allowing any excess to drip off. Place the dipped rings on a non-stick cookie sheet. This step is essential for getting that perfect crispy texture.
Lightly spray or drizzle extra-virgin olive oil over the onion rings. This will help them brown beautifully in the oven.
Bake the onion rings in the preheated oven. After 10 minutes, flip them to ensure even baking. Continue baking until they are golden and crispy, about 10 to 15 more minutes.