Line 2 half-sheet pans with silpats, parchment paper or non-stick foil. Preheat oven to 250°F.
Combine brown sugar, butter, corn syrup, vanilla and salt in a heavy, medium-sized saucepan over medium high heat. Bring to a boil. Boil for 5 minutes, stirring occasionally. Remove the pan from the heat and add the baking soda. It will foam up big time! Don't worry, it's to be expected.
Combine the rice or corn chex and pretzel sticks in a very large mixing bowl. Pour the molten caramel over the goodies in the bowl and stir very gently but thoroughly to evenly coat. Don’t worry about perfection here: just try to get the caramel mixture evenly distributed.
Split the mixture between the two prepared pans and spread it out evenly. Bake in the oven for 1 hour, stirring well every 15 minutes. If the mixture is still quite damp in the middle, you may need to bake it another 15-30 minutes, still stirring after every 15 minutes. When it is mostly dry but still a little sticky, it is done.
As soon as it comes out of the oven, stir well but gently once. Sprinkle the bits o’ brickle over the tops of the pan then the chocolate chips, using half of each over each pan. Let it cool on the pan (you may hear it crackling as it cools), break it up, and store in an airtight container at room temperature.