Combine the Cheerios, Rice Chex, Corn Chex, M&M's, nuts, pretzels, and cacao nibs in your largest mixing bowl.
Combine the white chocolate and espresso powder in a medium microwave-safe bowl. Microwave on high power in 30-second increments, stirring between each with a silicone spatula. This should take about 5 increments for the chocolate to melt and look smooth. In the meantime, roll out a couple large sheets of wax or parchment paper on a work surface away from direct sunlight.
Pour the melted chocolate over the cereal mixture and mix very well with a large silicone spatula, or better yet, with your hands. It gets a little messy, so if you have food-safe disposable gloves on hand put those...on hands.
Divide the mixture in half and spread evenly on the wax or parchment paper. Leave it for 30 minutes to set up before storing in airtight containers.