Line a baking sheet with parchment paper, and preheat oven to 250 degrees F.
In a large mixing bowl, toss together cereal, pretzels, and nuts (I used roasted, salted almond and peanuts and raw pecans). Do whatever you want.
In a 3-quart size saucepan, melt butter over low heat, and add brown sugar, corn syrup, and salt. Turn heat up to medium, and stirring constantly, bring to a boil. Boil for 2 minutes, and remove from heat. Add vanilla and baking soda, and completely incorporate. The mixture will begin to foam.
Quickly pour over cereal mixture, and stir to coat. Don’t worry if all pieces aren’t completely covered because this will happen as the mix bakes in the oven.
Transfer to parchment-lined baking sheet, spreading evenly, and bake for 1 hour, stirring every 15 minutes.
Remove from oven, and continue stirring to keep the clumps separated. If you have a heat-proof counter or surface to work on, transfer the mix to it, and separate the clumps as much as possible. If you want to add some sea salt, now is the time to sprinkle it all over.
It will be very hot, but as soon as you can handle touching it, use your fingers to break the pieces apart. Then allow them to cool completely. Store in an airtight container.