"Top Tier" Devil's Food Cake with Sour Cream-Fudge Frosting

Ingredients in this Recipe

1 large egg
1 ounce high quality milk chocolate (such as Lindt, Perugina, or Valrhona), chopped
1/2 teaspoon baking soda
1/2 teaspoon vanilla extract
1/3 cup (packed) dark brown sugar
1/4 cup (1/2 stick) unsalted butter, room temperature
1/4 cup boiling water
1/4 cup buttermilk
1/4 cup canola oil
1/4 cup natural unsweetened cocoa powder
1/4 cup sugar
1/4 teaspoon salt
2/3 cup cake flour
2/3 cup sour cream
4 teaspoons light corn syrup

See Full Recipe at Epicurious