Pre-heat the oven to 350°F or gas mark 4. Line the bottom of the spring form pan with parchment paper.
In a food processor add the graham cracker sheets and pulse until they are turned to crumbs.
Add the butter, sugar, and cinnamon and pulse until all ingredients and combined thoroughly.
Spread out the crumbs evenly on the bottom of the springform pan and bake for 8 min. Remove from the oven to cool.
Making the brownie
While the crust is baking in the oven, on medium heat melt the butter in a saucepan.
Once the butter has completely melted add espresso and cocoa powder. Mix until completely blended not letting the butter boil.
Remove from the heat and using a rubber spatula stir in the sugars until they are blended.
Add the eggs one at a time until blended. Be sure to not overmix.
Once all of the eggs are added pour in the flour, vanilla, and salt. Mix until combined, add the chocolate chips, and then pour into the graham cracker crust.
Reduce the heat to 325°F or gas mark 3.
Bake for 1 hour or until a toothpick or knife inserted in the center comes out clean. Remove from the oven and allow to cool on a rack.
Making the marshmallow fluff
In a saucepan add the sugar, water, and corn syrup. Stir the mixture until the sugar is evenly mixed.
Place on medium-high heat and bring to a boil. Once the sugar has dissolved do not stir otherwise crystals may form.
Cook until sugar syrup reached 240°F or 116C. Remove from the heat.
In a stand mixer combine the egg whites and cream of tartar and whisk until soft peaks form about 3-5 minutes.
Slowly pour the sugar syrup into the egg whites. Once all of the syrup has been poured into the egg whites increase the speed to high and whisk. The egg whites will collapse and then increase in volume. Continue to whisk until the egg whites become light and glossy.
Remove cooled brownie from the pan and spread or pipe the marshmallow fluff on top.