Coat a 9x13 inch pan with butter or non-stick cooking spray. Measure out the cereal and set aside. Pour the marshmallows into a large bowl and set aside.
To make the browned butter: Melt the butter in a small pot over medium heat. Continue to cook, swirling the pan occasionally until the butter boils and turns golden brown and smells slightly nutty. Keep an eye on it because you don't want it to burn. This could take 5-10 minutes.
Once the butter is brown and nutty, immediately pour it into the large bowl over the marshmallows- some brown bits may go with it, and that's okay. Stir to combine then place the entire bowl in the microwave for 30 seconds. Stir and reheat for an additional 30 seconds until the marshmallows have completely melted. Be careful because the mixture will be hot. Repeat if necessary.
Stir the cinnamon, nutmeg and ginger into the marshmallow mixture and mix until combined. Quickly add the cereal to the marshmallow-spice mixture and stir until everything is well coated. Working quickly, scrape the mixture into your prepared dish. With buttered hands, press the cereal evenly into the corners and smooth the top.
Let cool completely and cut into bars.