Instructions:
- Preheat oven to 250°F (120°C). Line two large baking sheets with parchment paper.
- In a large mixing bowl, gently combine the Chex cereals, pretzels, and nuts.
- In a medium saucepan over medium heat, combine the butter, brown sugar, and corn syrup. Bring to a gentle boil, stirring constantly until the sugar is completely dissolved (about 3 minutes).
- Remove the saucepan from the heat immediately. Whisk in the vanilla extract, then quickly whisk in the sifted baking soda. The mixture will foam up.
- Pour the hot toffee mixture evenly over the cereal base in the large bowl. Use a rubber spatula to gently fold and toss until every piece is lightly coated.
- Spread the coated mix in a thin, even layer across the prepared baking sheets. Bake for 20 minutes, stirring gently halfway through (at the 10-minute mark).
- Continue baking for another 15–20 minutes, stirring every 10 minutes, until the mix is a rich, deep golden brown.
- Remove from the oven and immediately transfer the mix back into the large clean bowl (or spread onto fresh parchment). While still hot, sprinkle both sets of chocolate chips over the top. Let it sit undisturbed for 5 minutes to allow the residual heat to melt the chips.
- Gently stir until the chocolate is mostly melted and glossy. Immediately scatter the festive sprinkles over the mix.
- Allow the mix to cool completely at room temperature (about 30 minutes) until the toffee is fully hardened and 'cracked.' Break into pieces and store in an airtight container.