Canola oil, for frying
1 tbsp. fish sauce
1 tbsp. fresh lemon juice
1 tbsp. hot chile oil
1/2 tart apple, such as granny smith, minced
1 pound medium brussels sprouts, trimmed
2 tbsp. grated pecorino romano
1 teaspoon black sesame seeds
1 teaspoon minced chives
Heat 2" canola oil in a 6-qt. saucepan until a deep-fry thermometer reads 375°.
Stir fish sauce, lemon juice, chile oil, and apple in a large bowl; set sauce aside.
Working with 1 sprout at a time, use a paring knife to cut an "x" halfway through stem end, keeping sprout intact.
Working in batches, fry sprouts until golden brown and slightly crisp, 2–3 minutes. Using a slotted spoon, transfer sprouts to paper towels to drain.
Add sprouts to bowl with sauce and toss to combine. Transfer to a serving platter; garnish with Pecorino, sesame seeds, and chives.
