Black and White Cupcakes

I'm a fan of the cupcake.  I'm a fan of the Black and White shake.  There's nothing wrong with this.  Recipe from the New York Times Magazine.

Black and White Cupcakes
Yield: 18 cupcakes

Ingredients for the cupcakes

• 1 3/4 cups all-purpose flour
• 2 tsp baking powder
• 1/4 tsp baking soda
• 1/4 tsp fine sea salt
• 10 tbsp unsalted butter, at room temperature
• 1 cup sugar
• 3 large eggs
• 1 large yolk
• 2 tsp pure vanilla extract
• 3/4 cup buttermilk, shaken
• 1 cup mini chocolate chips

Ingredients for the frosting

• 9 ounces semi-sweet or bittersweet chocolate, finely chopped
• 3 tbsp confectioner's sugar, sifted
• 6 tbsp cold unsalted butter
• sprinkles, optional (are sprinkles ever really optional?)

Instructions

1. To make the cupcakes: Position the racks to divide the oven into thirds, and preheat to 350.  Line 18 muffin cups with cupcake papers, or grease the tins.
2. Whisk together the flour, baking powder, baking soda, and salt.
3. Working with a mixer, beat the butter and sugar together on medium speed until light and fluffy, 3-4 minutes.  Add the whole eggs and the yolk one at a time, mixing well after each goes in.  Beat in the vanilla.
4. On low speed mix in the dry ingredients in three additions and the buttermilk in two, scraping the bowl, as needed, and beating until the batter is smooth.  Mix in the chips.
5. Divide the batter among the muffin cup.  Bake for 20-22 minutes - rotating the pans top to bottom and front to back  after 10 minutes - or until the tops feel springy to the touch (they won't color much) and a toothpick inserted into the center comes out clean.  Cool in the pans for 10 minutes, then transfer to a rack to cool to room temperature.  Frost, and cover with sprinkles, if you'd like, before the frosting dries.
6. To make the frosting: Put the chocolate in a heatproof bowl, and fit it into a saucepan or simmering water - don't let the bottom of the bowl touch the water.  Melt the chocolate, stirring occasionally.  Remove the bowl from the heat, whisk in the sugar and let rest on the counter for three minutes.  Bit by bit, whisk in the cold butter, mixing until smooth and thickened enough to spread.  Use immediately.