Instructions

In a mixer, cream butter and sugar together for about 4 minutes. Add sour cream and vanilla extract and mix until combined.

Add the egg whites and combine well.

Combine dry ingredients in a separate bowl.

In a measuring cup, combine milk and water.

Add half the dry ingredients to the mixer.

Then add the milk/water and finish with the rest of the dry ingredients. Mix until combined, scraping the bottom of the mixing bowl a couple of times.

Fill cupcake liners 1/2-2/3 full and bake 15-18 minutes. Cool.

To make the pastry cream, put yolks in a bowl and whisk well.

Put the sugar, cornstarch, and milk in a saucepan and cook on medium until the mixture starts to thicken while whisking constantly.

Lower the heat and simmer for 2 minutes then remove from the heat.

Add a little of the hot mixture to the yolks whisking continuously so the yolks don't cook.

Add the mixture all back into the pot and bring to a gentle boil. Cook 2 mins while stirring.

Remove heat and stir in butter/vanilla. Cover surface with plastic and cool..

To make the ganache, bring the cream to a boil and it pour over the chocolate and corn syrup in a heatproof bowl.

Cover and let sit a few mins and then whisk.

Chill 2 hours until completely cool.

Assembly,

Cut out centers and fill with pastry cream. Replace top with a small piece of cake you cut out.

Pipe on the ganache!

Ateco tip 844 is the best! Even better than my Wilton 1M!

Store in fridge.t.  Add chopped chocolate, and let stand till chocolate starts to melt.  Stir until smooth.