Preheat your oven to 325°F (160°C). In a mixing bowl, combine graham cracker crumbs, unsweetened cocoa powder, brown sugar, and melted butter, stirring until well blended. Press this mixture firmly into the bottom of a springform pan to create an even crust.

Bake for 10 minutes until set, then remove from oven and allow to cool completely.

In a large mixing bowl, beat softened cream cheese with an electric mixer on medium speed until smooth and creamy, about 2-3 minutes. Gradually add granulated sugar, continuing to mix until fully incorporated.

Next, add vanilla extract and salt, blending for another minute until the mixture is velvety and without lumps.

With the mixer on low speed, add the eggs one at a time, mixing gently after each addition just until combined.

Slowly pour in the cooled brewed espresso or strong coffee, along with coffee liqueur if desired, mixing on low speed until the batter is completely smooth and uniform.

Pour the luscious filling over the cooled crust, smoothing out the top with a spatula. Carefully transfer the pan to the preheated oven and bake for 55-60 minutes.

Once baking is complete, turn off the oven and crack the door open, allowing the cheesecake to cool slowly inside for 1 hour. Afterwards, transfer to the refrigerator for at least 4 hours or preferably overnight.

Once chilled, carefully run a knife around the edges of the springform pan to loosen the cheesecake. Remove the sides of the pan gently.

For the finishing touch, garnish with chocolate shavings or whole coffee beans if desired. Slice into pieces and serve chilled.