Prepare a square 8x8 baking dish with parchment and grease. Set aside.
In a medium or large-sized saucepan, melt the butter until it browns on medium-low heat. The butter will melt, turn a golden color, slightly foam, and then brown. This process will take about 3-6 minutes. Stir the butter periodically, but keep a close watch on it. Once it gets to the browning process, it happens fast and can burn quickly.
While the butter is browning prepare the espresso however you would like.
When the butter is brown, remove it from the heat and add in the espresso and the Baileys. Add the mixture in carefully, as it might spatter when it hits the butter. Mix it quickly to combine and set it back on the heat.
Slowly add in the marshmallows, starting with 1 and ½ bags. Mix until melted over medium heat. Don't rush the process and up the heat. Be patient, otherwise, everything will burn.
When the marshmallows look soupy, fold in the cereal. You'll have to work quickly in this process before the cereal starts to harden from the marshmallows. If there is too much marshmallow mixture, add in more cereal if needed. You can also add in more marshmallows if needed.
Add the cereal mixture to the dish and use a spatula to make an even layer. Use your hands or a sheet of parchment to make a flat and even layer. If everything sticks to the spatula, spray it with some cooking spray. It will help everything make a smooth transition from the pot to the dish without everything sticking to each other.
Let the treats sit in the pan and cool completely for about 30 minutes. When ready, cut into large squares to serve.
