Baked Onion Rings

We've gotten heaps of onions from the farm this year. Last year I chopped them in the food processor and stored them in the freezer. But haven't gotten around to that this year. So...we tried these Baked Onion Rings slightly adapted from Allrecipes.com. Quite good and could easily become a late night snack.

2 medium yellow onions (I actually did 3 and have tons of slices leftover that we didn't have enough crumbs for...could be that 1 is plenty)
3 egg whites
1 cup dry bread crumbs
2 tsp dried thyme
1 tsp salt
1/8 tsp dried chipotle spice
1/8 tsp pepper

Slice onions ~1/4 in thick using mandolin (this is the thickest setting on my mandolin), separate rings and place in bowl. Cover with ice water, soak for 30 minutes. Drain.

In a small bowl beat egg whites until foamy (and starting to thicken). In another bowl combine remaining dry ingredients. Divide crumb mixture between 2 bowls. Dip onion into egg whites and then into crumb mixture shaking bowl till onion is coated. Place on a baking sheet coated with nonstick cooking spray. Bake at 400 degrees for 20 minutes.