Preheat oven to 375°F/190°C.
In a medium stainless steel bowl, mix the graham crumbs, cocoa powder and melted butter until well combined.
Line 6 muffin cups of a large muffin pan. Divide the graham crumb mixture between the 6 cups. Press the mixture into the cup to create an even crust with a well in the middle.
Place the muffin pan in a preheated oven for 10 - 12 minutes or until the shells are slightly crisp to the touch. Remove pan from the oven and set aside. Allow the graham crusts to cool.
Place a saucepan with 2 in. of water on the stove to simmer. In a medium size stainless steel bowl or double boiler, add lemon juice, sugar, lemon zest and eggs and whisk mixture until foamy. Set mixture over simmering water and continue to whisk. Ensure the bowl or double boiler does not touch the water or lemon curd will overcook.
Whisk curd until it reaches a spoon-coating consistency. Remove double boiler from the heat, add the butter and mix until completely incorporated. Set aside mix and allow it to cool.
Remove chocolate crusts from muffin molds and place a dollop of the lemon curd in the well of each crust. Garnish with a sprig of mint and/or a few fresh berries.