Butter a 9 x 13 baking pan.
In a large sauce pan, melt the butter over low heat. As the butter melts, slice the vanilla bean in half lengthwise and scrape the seeds directly into the butter.
Once the butter has melted, it will start to bubble and crackle. Watch carefully to see it slowly brown. As soon as the bubbling subsides, after about 5 minutes, the butter will be browned. Add the marshmallows and a pinch of salt and stir constantly over low heat until the marshmallows are completely melted and the vanilla seeds are evenly distributed.
Remove the pan from the heat, add the cereal, and mix well to combine. Turn the mixture into the prepared pan and pat into an even layer. allow to cool for about an hour, or to room temperature, then cut into even pieces.
Treats can be stored in an airtight container for up to 2 days