Make the frosting:
In a double boiler, melt the chocolate carefully. In a blender, blend the evaporated milk, sugar, and salt until the sugar is dissolved. Add the chocolate and blend until the mixture is thick and glossy, about 3 minutes. Store at room temperature, covered with plastic, until ready to use.
Bake the cupcakes:
Heat the oven to 350°F. Grease your muffin tins. Melt the chocolate carefully in a double boiler; set aside to cool.
Sift the flour, baking soda, salt, and sugar into a medium bowl. In a large bowl, whisk the coffee, sour cream, oil, and eggs; whisk in the chocolate. Add the dry ingredients, whisking until there are no lumps.
Pour the batter into the prepared muffin tins, portioning it evenly to make 16 cupcakes. Bake on the middle rack until a toothpick inserted into the middle of a cupcake comes out clean, 19 to 20 minutes. Let the cupcakes cool in the pan for 15 minutes; then remove them from the pan and let them cool completely. Spread the cupcakes generously with the frosting.
Make Ahead Tips
The frosting can be made up to two days ahead and kept covered at room temperature
nutrition information (per serving):
Photo: Alan Richardson