Use to make GILT chef Justin Bogle's Spring Salad with Mushroom ''Dirt''.
Preheat oven to 180 degrees. Line a baking sheet with a nonstick baking mat; set aside.
Place glucose, 6 tablespoons water, salt, and citric acid in a small saucepan and bring to a simmer over medium heat. Remove from heat and let cool.
Place fennel in an even layer in a vacuum bag; add glucose solution and seal on highest setting of a vaccum sealer. Let stand for at least 5 minutes. Remove fennel from bag and pat dry.
Spray prepared baking sheet with nonstick cooking spray; wipe off any excess. Lay fennel slices in an even layer on baking sheet; top fennel with a second nonstick baking mat. Transfer to oven and bake for 10 minutes. Remove second nonstick baking mat and continue baking until fennel is dry and crisp, about 1 hour.