How to Make It
Preheat oven to 300°F. Line 2 baking sheets with parchment paper.
Place cereal squares, corn snacks, pretzels, bagel chips, peanuts, and peas in a large bowl.
Melt butter in a small saucepan over medium. Remove from heat, then whisk in honey, dry mustard, Dijon mustard, chili powder, onion powder, salt, and cayenne, if using, until combined.
Drizzle butter mixture over cereal mixture; gently stir together until well combined, then spread onto prepared baking pans. Bake, stirring every 10 minutes, until fragrant and lightly toasted, about 30 minutes. Let cool 10 minutes before serving. Snack mix keeps, in airtight containers at room temperature, for up to 2 weeks. Recrisp if necessary.