1. Start frosting: Place chocolate chips and salt in a medium, heat-proof bowl. Pour cream into small pot over medium-high heat and bring to a boil. Pour cream over the chocolate, then add vanilla, and whisk until smooth. Let mixture cool to room temperature.
2. Meanwhile, heat oven to 350 degrees F. 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.
3. Using mixer, cream the sugar and butter at medium speed until light and fluffy, about 3 minutes. Beat in eggs, one at a time, for a full minute after adding each egg.
4. Reduce the mixer's speed to low and add a third of the dry ingredients to batter, followed by half the buttermilk mixture. Mix until the dry ingredients disappear, then repeat twice more until all the ingredients are added. Scrape bowl, then beat on low for 10 seconds. Add boiling water and mix on low until well blended.
5. Fill each muffin well two-thirds full with batter. Bake until the tops feel firm, about 20 minutes. Let the cupcakes cool in the pan for 15 minutes; transfer to cooling rack.
6. Finish the frosting by using a mixer with the whisk attachment set on medium-high speed to beat the chocolate mixture until light and fluffy, about 4 minutes. Frost cupcakes right away.