1large egg plus 1 egg yolkboth at room temperature
1/2cupfirmly packed brown sugar
1/2cupbuttermelted but starting to cool
1/2cupbuttersoftened but not melted
1/3cupdark cocoa powder
1/3cupmilkhalf and half or heavy cream (I use half and half)
Pinchof salt if desired for taste
Preheat oven to 350 degrees F.
Line muffin pan with 12 cupcake wrappers.
In a large bowl, combine cocoa powder, flour, baking soda and salt. Mix well and set aside.
In a separate bowl, combine egg, egg yolk and sugars. Mix well by hand to combine. STir in milk and sour cream, stirring well to combine. Add in coffee and butter, mixing well to combine. Mix with dry ingredients until well combined.
Fill liners with cupcake batter, approximately 3/4 of the way full.
Bake for 15-20 minutes or until cupcakes bounce back when lightly pressed and toothpick inserted into center comes out clean. Remove from oven and allow to cool for at least 30 minutes prior to frosting.
Beat butter in bowl until creamy. Add in cocoa and mix well to combine. Add half the powdered sugar and half the milk and beat well until combined, then add remaining powdered sugar, milk, vanilla and salt, beating well for approximately 2-3 minutes. If needed more milk can be added to thin frosting or more powdered sugar can be added to thicken frosting to reach desired consistency. Once cupcakes are completely cool, frost.