First, start the frosting. Place the chocolate chips and salt in a medium, heat-proof bowl. Pour the cream into a small pot over medium-high heat, and bring it just to a boil. Carefully pour the cream over the chocolate, then add the vanilla and whisk it until it's smooth and shiny. Let the mixture cool to room temperature, about 1 hour.
Meanwhile, heat the oven to 350°. Line 18 muffin wells with paper liners. In a small bowl, stir together the buttermilk and vanilla. In a medium bowl, whisk together the next five ingredients. Set both bowls aside.
Using a hand or stand mixer, cream the sugar and butter at medium speed until light and fluffy, about 3 minutes. Beat in the eggs, one at a time, for a full minute after each addition.
Reduce the mixer's speed to low and add one third of the dry ingredients to the batter, followed by half of the buttermilk mixture. Mix until the dry ingredients disappear, then repeat twice more until all the ingredients are added. Use a bowl scraper or rubber spatula to scrape the bowl, then beat on low for 10 more seconds. Add the boiling water and mix on low until well blended.
Fill each muffin well two-thirds full with batter. Bake until the tops feel firm when you press them and a toothpick test yields a done result, about 20 minutes. Let the cupcakes cool in the pan for 15 minutes, then transfer them to a cooling rack to cool completely.
Finish the frosting by using a hand or stand mixer with the whisk attachment set on medium-high speed to beat the chocolate mixture until light and fluffy, about 4 minutes. Frost the cupcakes right away.