Preheat oven to 350 degrees F.
For the cupcakes:
Line mini cupcake pans with mini paper liners and set aside.
Sift together the dry ingredients. Set aside.
In a saucepan bring stout to a boil and continue boiling for 2 minutes. Remove from heat. Stir in coconut butter to melt. Add lemon juice and allow to cool slightly, until mixture is lukewarm. Stir in sweetened condensed milk and whisk in the lightly beaten egg. Add the wet mixture to the dry ingredients and stir until just combined.
Distribute batter among the lined mini cupcake pans, filling each about 1/2 full. Stand a chocolate shard directly in the center of each cup. Place in the oven and bake for about 15 minutes. When cool enough to handle, remove cupcakes from the pan and set on a cooling rack to cool completely.
For the pretzel crumbles:
Preheat the oven to 375 degrees F.
Mix together the flour, sugar, cayenne pepper, and salt. Using fingers, work in butter and then the crushed pretzels to create a coarse crumble. Spread the mixture onto a parchment-lined baking sheet. And bake for 12-14 minutes, gently stirring once halfway through baking. Remove from the oven and set aside to cool.
For the frosting:
In a double boiler or a heat proof bowl, combine all the ingredients except for the butter and sugar. Melt the mixture, stirring continuously until very thick, about 12 minutes. Remove the mixture from the heat and strain through a sieve to remove any lumps. Cool completely. Once the malt mixture has cooled, cream together with the butter. Incorporate the sugar and whip thoroughly, scraping down the sides of the bowl as you add the sugar.
To assemble: Using a 3/8 inch pastry tip, pipe a "donut" of frosting encircling the "belly button" of the cupcake. Top each cupcake with the spicy pretzel crumbles and serve.