INGREDIENTS
1
Egg yolk plus, large
2 1/4 cups
All-purpose flour
1 1/2 tsp
Baking soda
8 oz
Bittersweet chocolate
1/3 cup
Brown sugar, packed light
1 1/8 cups
Granulated sugar
1
Milk chocolate frosting
2 1/2 tsp
Salt, coarse
1 tbsp
Vanilla extract, pure
1 1/2 sticks
Butter, unsalted
1 1/2 cups
Sour cream
3/4 cup
Whole milk