Combine chex, grahams, and nuts in a large baking pan with sides.

Melt butter and stir in vanilla and brown sugar. Pour butter mixture over dry ingredients and stir to coat.

Bake 250 30 min, stirring every after 15 minutes.

Toss the chips onto the hot mix and let sit for 1 minute to begin melting. Gently toss and stir mix to distribute the melting chips.

Cool and refrigerate to harden.