In a large, heavy-bottomed pot, melt butter over medium heat.
Once melted, add in herbs and continue cooking, stirring constantly, until it begins to foam.
Keep stirring until milk solids have caramelized.
Remove herbs and add in marshmallows, stirring constantly until melted.
Turn off the heat and add in cereals and nuts.
Stir to combine.
Stir in mini marshmallows.
Transfer mixture to a parchment lined 9x9 baking dish.
Press into an even layer using parchment paper.
Garnish with thyme leaves and flaky sea salt.
Allow to cool.
Cut into squares and serve.
