3. Make the potatoes: Bring potatoes to a boil in a large pot of salted water; cook until just tender, 8–10 minutes. Drain potatoes and spread on paper towels to dry. Heat 2″ oil in a 6-qt. saucepan until a deep-fry thermometer reads 375°. Working in batches, fry potatoes, bell pepper, and onion until crisp, about 7 minutes for potatoes, 4 minutes for pepper, and 2 minutes for onion. Using a slotted spoon, transfer mixture to paper towels to drain. Place in a bowl and add coriander, fennel, salt, and pepper; toss to combine.