Line a 9-inch (23 cm) square pan with parchment leaving overhang for easy removal. Tear a small second sheet of parchment and set aside.

In a large saucepan or Dutch oven with a light-coloured interior melt the butter over medium heat. Once the butter has melted, gently swirl the pot and continue to cook until the butter has browned. The butter is finished when it has turned dark amber and smells nutty.

Turn off the heat, and stir in the marshmallows. The residual will melt mini marshmallows, but large marshmallows might require the heat to be turned to low.

When the marshmallows are melted and smooth, remove the pot from the heat and stir in the rice cereal, mixing to coat well.

Working quickly, transfer the mixture into the prepared pan, place the second parchment sheet on top and press the mixture flat with the palm of your hand. Be sure to press the mixture into the edges of the pan as well.

Let cool to room temperature, about 30 minutes.  Remove from pan using the parchment overhang, and cut into squares.

Store in an airtight container at room temperature.