Start cleaning the barbecue with your grill cleaning brush. Heat up your Kamado to 150 °C and place the pro set. Put both heat deflectors in the bottom of the pro set and place the grill grid on top at the highest level of the multilevel lift. After this, let your Kamado heat up further to 180 °C. Then grease the pan or baking tin with butter and heat it on the grid. Break the chocolate into small pieces and add these to the butter together with the espresso. Melt the chocolate in the butter. Then beat the eggs with the sugar until you have a light mixture. Add the chocolate to the egg mixture and fold it in. Then sift in the flour and mix everything again. Then add everything to the baking tin. Bake the brownie for 25 minutes on indirect heat. Place the marshmallows on top of the brownie and bake for another 5 minutes until the marshmallows start to melt.