Melt butter in your saucepan over medium heat, stirring frequently. I recommend a stainless steel saucepan. Once melted, it should start to foam up and audibly make popping/crackling noises. Once the noise stops, continue to swirl the pan until the butter develops a nutty aroma and brown bits start to form at the bottom. Don't move your pan too much, as you want the milk solids to be able to brown on the bottom.

Once the bits are amber in color, about 2 to 3 minutes after the crackling sounds have stopped, remove from heat.

Stir in marshmallows and mix well until fully incorporated. Then add vanilla and mix until you have a smooth, glossy marshmallow creme.

Pour over your rice krispies cereal and mix well to combine, but work quickly as it will get sticky and hard to work with as it cools.

Pour mixture into a parchment lined (or well-sprayed) 9x9 pan and press down to form your cereal treats. Top with flaked salt and let them cool/set for an hour or two. Then cut into 12 and enjoy!

Store leftovers in an airtight container at room temperature for up to 2 days.