Preheat the oven to 400 degrees and line a cookie sheet with parchment paper.
Add chex, pretzels and peanuts to a large mixing bowl.
In a saucepan over medium heat combine brown sugar and butter. Bring to a boil and boil for 3 full minutes stirring almost continuously until the sugar reaches 270-290.
Remove from heat and stir in vanilla and salt.
Pour the sugar mixture over the chex mixture evenly then stir to coat evenly.
Pour onto a cookie sheet and spread it evenly out.
Place in the oven for about 8 minutes, until bubbly.
Remove from the oven and then sprinkle with chocolate chips and m&ms.