Combine cereal, cashews, and banana chips in a large bowl.
Cook oil and mustard seeds in a small covered frying pan over medium heat until seeds pop, 1 to 2 minutes. Remove from heat and stir in remaining ingredients. Scrape from pan over cereal and mix to coat.
*Find in the baking aisle.
Make ahead: Store airtight up to 1 week.
Note: Nutritional analysis is per 1/2 cup.