Preheat oven to 375 degrees or preheat air-fryer to 400 degrees. If baking, coat a baking pan with cooking spray or line pan with parchment paper.
Drain thawed spinach. Wrap in paper towels and squeeze until all excess water is removed.
In a medium bowl, add spinach and all other ingredients, except wonton wrappers and egg white. Mix thoroughly.
Set up a work station with a small bowl of warm water. Place 1 tablespoon of spinach/cheese filling in the center of a wonton wrapper. Dip your fingers in the bowl of warm water and moisten edges of the wrapper. Pull two opposite corners of the wrapper up, over the filling, and pinch together. Repeat with the two remaining corners and pinch edges together to seal. Continue to do this to create 20 wontons.
Once all wontons have been prepared, lightly brush the wontons with the egg white.
To Bake them in Oven: Place all on the baking pan. Coat the tops with olive oil spray. Bake for 10 to 11 minutes, until the wontons are lightly brown.
To Bake in Air-fryer: Coat inside of air-fryer with olive oil cooking spray. Line 10 wontons in bottom of basket. It’s ok to overlap a bit. Spray the tops with olive oil spray. Bake for 6-8 minutes until golden brown. Remove from air-fryer and repeat instructions with remaining 10 wontons.
Serve warm. Store any leftovers in the fridge. Reheat in oven or microwave. These also freeze great! You can remove from freezer as many as you’d like to serve. Defrost in microwave. Can crisp up in oven or toaster oven.