Instructions
Place cereal in an extra large bowl, set aside.
Place sweetened condensed milk, baking chips, lemon juice, and zest in a medium saucepan. Slowly melt the chips over low heat, stirring frequently, until melted. During the last few seconds of the melting process, begin whisking the mixture to thoroughly combine the ingredients. The result should be a thick, syrup-like consistency.
Drizzle the mixture over the cereal, vigorously tossing to coat.
Transfer the coated cereal to large zipper bags (we found that 2, gallon-sized, zipper bags did the trick), divide the powdered sugar between the bags, seal, and gently shake until all of the Chex are coated.
Line 2-3 large baking sheets with wax or parchment paper, remove the coated cereal from the bags, and spread out in a single layer on the prepared baking sheets.
Let rest at room temperature, in as little humidity as possible, until dry and crunchy.
Once dry, you can store the snack mix in new zipper bags at room temperature.