Preheat oven to 300 degrees F and prepare 3 baking trays with grease and foil or parchment paper.
While oven is heating, remove stems from Mustard Greens and add greens to a salad spinner. Fill spinner with cooling water and wash greens.
Strain greens. Dry greens by blotting with a paper towel. Then tear the greens into smaller pieces and add into a large Zip-Lock bag with the olive oil.
Close bag and vigorously shake to coat all leaves with the oil.
Add pieces of Mustard Greens to baking trays making sure that each leaf is NOT touching another leaf. If greens touch, it will prevent the green from dehydrating properly and will become soggy instead of turning into a crispy chip.
Bake at 300 degrees F for 15-20 minutes, halfway through, swap trays onto their opposite levels. If tray one is on the lowest rack, and tray 2 and 3 are on the upper racks, halfway through, trade rack placement. You may find that some cook faster then others, and if that is the case take those chips out of the oven to cool.
Remove from oven and let cool. Once cooled enjoy. Store in the fridge in a covered bowl. These chips will stay fresh for up to 2 days.