To make the cupcakes: Preheat the oven to 350°F (175° C). Line 12-cup muffin pan with cupcake liners.
In a small bowl, whisk together flour, sugar, cocoa powder, baking soda, baking powder and salt.
In a medium bowl, whisk eggs, buttermilk, oil and vanilla extract until well combined.
Add the dry ingredients and fold the batter until just combined.
Divide the batter into the prepared cupcake cups, about 1/4 cup of batter in each cupcake cup. (TIP: Use a large cookie scoop, to measure the batter. 1 large cookie scoop full of batter in each cupcake cup.)
Bake for 18-20 minutes, or until the inserted toothpick comes out clean. Cool completely.
To make whipped ganache frosting: Roughly chop chocolate with a sharp knife and place in a large bowl.
Heat heavy whipping cream in a microwave for 1-2 minutes, or until hot. (Alternatively, you can heat the cream on stovetop until almost boiling, but not quite to a boil.)
Pour hot cream over chopped chocolate and let it sit for good 2-3 minutes.
Add salt and whisk the mixture gently from the center, stirring in one direction and slowly incorporating cream into the chocolate, until it's nice and smooth, about 2 minutes. (NOTE: Here's detailed ganache tutorial.)
To whip the ganache: Cool ganache completely at room temperature, about 1 hour. Then place the cooled ganache into a mixing bowl with whisk attachment and whip until fluffy and doubled in size.
To assemble: Transfer the frosting into a pastry bag fitted with star tip. (I used Wilton 1M tip.) Pipe the frosting on cooled cupcakes. Decorate with sprinkles, if desired.