Put the Chex and pretzels in a large bowl. Mix the butter and brown sugar together in a smaller bowl, stir until combined and brown sugar has started to dissolve.

Pour some of the brown sugar butter into the bowl with the Chex and pretzels and stir. Continue adding more butter and stirring until it's coated with all the butter.

Spread this mixture onto two baking sheets in a single layer and bake in a 250-degree oven for 45 to 55 minutes, stirring a few times.

Sprinkle the chocolate chips over top and place back in the oven for another minute until chocolate is melted. Gently stir so the melted chocolate coats some of the Chex and pretzels. Add in peanuts and some kosher or Himalayan Sea salt and give it another quick mix.

Let cool (place in fridge or freezer if desired) and put back into the large bowl with the mini Reese's cups. Stir until combined and serve. Store leftovers in a covered container for up to 5 days.