For the cupcakes: Preheat the oven to 345 degrees F. Line a cupcake pan with liners.
Combine the sugar, flour, cocoa powder, baking powder and baking soda in a bowl. In a small pot over low heat warm up 1 cup water, the butter and espresso. Do not boil! Just melt the butter. Set aside to cool.
Combine the buttermilk, eggs and coffee mixture in a second bowl.
Combine the wet ingredients with the dry ingredients and mix with a whisk until smooth.
Scoop the batter into the cupcake liners and bake for 10 to 12 minutes. Check for doneness by inserting a toothpick into the cupcakes. If it comes out clean, they are done. Allow to cool.
For the ganache: In a small pot over low heat, mix the chocolate and cream until combined and smooth. Take off the heat.
Add the coffee liqueur if using and mix.
To assemble: Using a apple corer or a small spoon, scoop a small well halfway through in the center of the cupcakes. Spoon 1 teaspoon of the ganache into the well, as well as brush some over the top of the cupcakes. Fill a pastry bag with piping tip of your choice with Salted Caramel Buttercream. Pipe the buttercream directly on top of the cupcakes.
Garnish as you please.
Slowly heat the cream in a small pot over low heat.
While heating up the cream, in another pot over medium heat, add one third of the sugar and the salt and mix with a wooden spoon until liquid. Continue to add the remainder of the sugar in one-third increments. Once all the sugar is dissolved, continue to mix the caramel until it reaches a slightly darker brown color.
Turn off the heat and add the hot cream very slowly in increments while stirring. Be very careful to not burn yourself! Caramel is ready once the cream and caramel are smooth.
Transfer to a bowl for cooling. Allow 1 hour to cool at room temperature.
Add the cooled caramel mixture to a mixing bowl and with a paddle attachment on medium speed, add the butter in increments. Once the buttercream is smooth it is ready to be used.
