Add 2 tablespoons of raw sugar to the hot espresso, and stir to dissolve. Add 1 tablespoon of rum and mix. Cover and refrigerate until cool.
Preheat the oven to 350degreesF, and position a rack in the center of the oven. In a large bowl beat the eggs with a hand mixer until they're foamy. Continue to beat the eggs while adding 1 cup of raw sugar in a slow and steady stream. Add 1 tablespoon of rum, and continuously beat the egg mixture for 6 minutes, until pale and shiny. In another large bowl, use a wire mesh sieve to sift together the all-purpose flour and sea salt. Fold one third of the fl our mixture into the egg mixture. Repeat two more times until all the flour is incorporated into the egg mixture. Delicately fold in the melted unsalted butter. Divide the batter equally among 12 lined muffin cups. Cook for 15 to 20 minutes, or until the cupcakes are slightly golden around the edges and an inserted toothpick comes out clean. Remove the cupcakes from the oven, and cool them on a rack. When the cupcakes have cooled slightly, brush each one generously with the espresso glaze.
ESPRESSO MASCARPONE ICING:
In a medium sized bowl combine the mascarpone, icing sugar, and the rest of the espresso glaze. Beat with a hand mixer until the icing is stiff. Using a pastry bag with a round nozzle (or a butter knife), ice each cupcake with about 1/4 cup of the icing. Garnish each cupcake with 1 teaspoon of shaved dark chocolate. Place in the fridge for 1 hour to set.