Add the graham crackers and brown sugar to a food processor, process until just fine crumbs remain. While the mixer is running, add the melted butter until well combined.
Press into the bottom of a spring form pan in an even layer until well compacted.
Add the chocolate stout, cocoa, and chocolate chips to a microwave safe bowl, microwave on high until melted, stirring frequently, about 90 seconds.
In the bowl of a stand mixer add the vanilla, heavy cream, powdered sugar and salt. Beat on high until medium peaks form. Turn the mixer to low and slowly add the chocolate until combined. Stir until well combined.
Pour over the crust in an even layer.
Top with marshmallows, freeze until set, about 2 hours.
Before serving toast the marshmallows with a culinary torch until blacked to desired degree.