Preheat oven to 375 degrees F (190 C) and place oven rack in the center of the oven. Line two baking sheets with parchment paper (amount as original recipe is written // increase number of baking sheets or work in batches if making a larger quantity).
Thinly slice beets with a mandolin, getting them as consistently thin as possible. They should curl a little when cut. This will ensure even baking and crispiness.
Divide between two baking sheets and spray or very lightly drizzle with olive oil. Add a pinch of salt, pepper, and the rosemary. Toss to coat. Then arrange in a single layer, making sure the slices aren’t touching.
Bake for 15-20 minutes or until crispy and slightly brown. Be sure to watch closely past the 15 minute mark as they can burn quickly.
Remove from oven. Let cool slightly. Then serve.
Best when fresh. Leftovers will lose their crispiness.
*Adapted from Cozy Kitchen *Nutrition information is a rough estimate calculated with 1/2 tsp olive oil.