Place the pepperoni in a cold medium saucepan or deep sauté pan. Turn heat to medium and cook for 5–7 minutes until the fat renders and the slices are crisp. Remove with a slotted spoon and drain on paper towel. Leave about 30–45 mL (2–3 tbsp) of rendered fat in the pan.
Add the popcorn kernels to the hot pepperoni oil and stir to coat evenly. Cover with a lid and cook over medium heat, shaking the pan every 20–30 seconds, until popping slows to about 2 seconds between pops. Remove from heat immediately.
Roughly chop the crispy pepperoni slices.
In a small bowl, combine the chopped pepperoni, Parmigiano Reggiano, paprika, basil, oregano, crushed fennel seed, garlic powder, and chili flakes.
Transfer the hot popcorn to a large bowl. Sprinkle the seasoning mixture over the popcorn while tossing continuously so the warm oil helps it adhere. Taste and season with salt as needed.
