Preheat oven to 350°F. Add cupcake liners to a muffin pan and set aside.

In a large bowl, stir together flour, salt, baking powder, and cocoa powder.

In another bowl, cream butter and sugar with an electric mixer on medium speed.

Melt the chocolate chips in the microwave for about 40 seconds. Stir. Put back in for 20 second increments stirring in between until melted. Pour chocolate into butter/sugar mixture and mix on medium speed.

Add eggs and egg yolks one at a time while continuing to mix.

Add oil, vanilla, and sour cream and continue to mix on medium.

Add wet ingredients to dry ingredients and stir to combine.

Fill each cupcake liner about ¾ full.

Bake 23 to 25 minutes or until a toothpick comes out of the center of a cupcake clean. Cool in pan for 15 minutes before removing to a baking rack. Cool completely before frosting.

To make the frosting, add butter to a mixing bowl and beat until smooth. Add in half and half and vanilla extract and continue to beat with an electric mixer on medium.

Add in icing sugar and dark cocoa and beat until well blended.

Frost cupcakes and drizzle chocolate sauce over top, if desired.