Soak the sliced onions in the milk for about an hour.
Preheat the oven to 450degrees.
Dredge the soaked onions in the flour and shake of excess flour, as able.
Dip them back into the milk. A fork is usually best for this.
Dredge them through the panko breadcrumbs, use a fork to pick them off, shake off the excess, and place on cookie sheet.
Give the breaded slices a light spray of cooking spray.
Bake for about 12 minutes. Flip and continue baking for about another 10.