Preheat oven to 350°F and line a large baking sheet with parchment paper.

In a large bowl, combine the rice chex and rice krispies cereals. Set aside.

In a medium saucepan, melt the butter over medium heat. Stir in brown sugar, vanilla extract, cinnamon, and salt until dissolved.

Bring the mixture to a boil, stirring continuously. Continue boiling for 2-3 minutes, until it thickens and lightens in color.

Remove from heat and immediately pour the caramel mixture over the cereal. Toss to coat evenly.

Spread the coated cereal on the prepared baking sheet in an even layer. Bake for 7–9 minutes.

Allow the crackle to cool completely, then break into clusters. Store in an airtight container.