1) Preheat oven to 350 degrees. Line cupcake pans with paper liners. Set aside.

2) Whisk dry ingredients together in a mixing bowl.

3) Add eggs, milk, oil and vanilla. Using the paddle attachment, beat with a mixer on medium speed for 1-2 minutes, occasionally scraping the sides of the bowl with a rubber spatula.

Add the boiling water and beat, just until blended. (The batter will appear watery.)

4) Fill the liners with batter, until about 2/3 full. Bake for 12-16 minutes, until the center of the cupcakes spring back when lightly touched and an inserted toothpick comes out clean.

5) Cool in pan for 10 minutes. Remove cupcakes and place on a cooling rack. Allow cupcakes to cool completely before frosting.

6) Melt chocolate in microwave or double boiler, stirring often. Set aside to cool, until slightly warm.

7) Combine butter and salt with the paddle attachment. Beat until blended. Add powdered sugar and mix until well blended, 2-3 minutes.

8) Add vanilla and sour cream, blending until smooth. Add chocolate and mix until incorporated.

9) Insert a cake decorating tip of choice into a pastry bag. Place the bag into a tall glass and fold the open end of the bag over the sides. Fill bag with frosting.

Pipe frosting onto cupcakes, beginning on the outside and working to the center.

10) Top with chocolate chunks, chips, or shavings.