Chocolate Cupcakes with Creme Anglaise Buttercream

I tried to combine some of my favorite chocolate cakes.
I was going to decorate these as rabbits for the Chinese New Year.
Decided it was too much trouble with all the snow shoveling.

Makes 24 cupcakes

Cupcakes
2 1/2 c flour
1 1/4 c cocoa powder
2 1/2 tsp baking soda
1 1/4 tsp baking powder
1 1/4 tsp salt
10 T unsalted butter
2 1/2 c sugar
2 large eggs
1 egg white
1 T vanilla
1 cup sour cream
1 1/2 c milk

Buttercream
5 egg yolks
1/2 c milk
2/3 c sugar
1/4 tsp salt
1 tsp vanilla
3 sticks unsalted butter

Line two 12 cup muffin tins with cupcake liners.  Spray liners with cooking spray.  Whisk flour through salt.  Cream butter and sugar.  Beat in eggs and white, one at a time.  Beat in vanilla.  Alternate additions of flour with sour cream and milk, beginning and ending with flour.  Spoon batter in, not filling too far.  Bake at 350F for 30 minutes.  Cool.

Using the mixer whisk attachment, beat egg yolks with 1/3 c sugar until they hold a ribbon.  In a medium size saucepan, heat 1/2 c milk with 1/3 c sugar and 1/4 teaspoon salt to simmering.  With mixer on low, slowly add to egg yolks.  Return to stove top.  Cook on medium heat until it begins to boil.  Strain and pour back into mixing bowl.  Add vanilla.  With whisk attachment, mix until the eggs have doubled in volume.  Set aside.  Beat 3 sticks of butter until it slaps the side of the mixing bowl.  Slowly pour the eggs into the butter while continuing to mix.  Beat on high until smooth and shiny.