Prepare your pan with parchment paper, butter, or oil.
Brown your butter:Add butter to a large pot and place over medium heat. The butter will begin to crackle, and start to foam. Whisk constantly during at this point. After a couple of minutes, the butter will begin turn a golden amber color on the bottom of the saucepan. Once the butter browns add 10 cups (or 1½ bags) of the marshmallows to the pot. Stir the butter and marshmallows until the marshmallows are fully melted. This takes about 5 minutes (but can vary depending on you marshmallows).
Add bourbon, vanilla, and nutmeg. Let the mixture come to a slow boil. Remove from heat.
Add Rice Krispies and coat thoroughly.
Add remaining marshmallows. They should melt partially from the heat of the mixture. But still leave a few gooey chunks.
Pour rice krispie mixture into you prepared pan.
Let your Rice Krispie Treats stand for a least an hour to fully cool and set up.Enjoy!