Line a sheet pan with foil or parchment and preheat the oven to 325 degrees. In a large bowl, combine cereals, pretzels, almonds, peanuts, and toffee bits.

Melt the butter in a small saucepan over medium-high heat. Let cook until golden brown, about 5 minutes. Be careful to not let it burn.

Remove the butter from the heat and add the thyme. Be careful, it is going to splatter, stand back. Add the brown sugar, mustard, and salt. Mix well.

Add the butter mixture to the cereal and toss to coat.

Pour out into a single layer and bake for 15 minutes, or until the toffee bits melt.

Take out and toss. Remove the thyme sprigs and let cool completely.