Preheat oven to 350°F. Line a muffin tin with cupcake liners.

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

In another bowl, beat together butter and sugar until creamy.

Melt chocolate chips in microwave, stir until smooth, and add to butter mixture. Mix well.

Add eggs and egg yolks one at a time, mixing well after each addition.

Mix in oil, vanilla, and sour cream until combined.

Gradually add dry ingredients to wet ingredients, mixing until just combined.

Fill cupcake liners about 3/4 full with batter.

Bake for 23 to 25 minutes, or until a toothpick inserted in the center comes out clean.

Allow cupcakes to cool completely. Prepare frosting by beating butter until smooth. Mix in half and half and vanilla. Add powdered sugar and cocoa, beat until fluffy.

Frost cooled cupcakes. Drizzle with chocolate sauce if desired.