Place the chopped chocolate in a heatproof bowl or the top of a double boiler placed over, but not touching, barely simmering water. Stir until the chocolate is melted and smooth. Remove from the water and set aside to cool slightly.
Preheat oven to 350 deg F.
Prepare pans with cupcake liners
Sift the flour, baking powder, baking soda, and salt into a medium bowl and set aside.
In a large bowl, using an electric mixer on medium speed, beat the butter and sugar until smoothly blended and creamy, about 2 minutes. Stop the mixer and scrape the sides of the bowl as needed during mixing.
On low speed, mix in the melted and cooled chocolate. On medium speed, add the eggs one at a time, mixing until each is blended into the batter. Add the vanilla and beat until the mixture looks creamy and the color has lightened slightly, about 1 minute.
Mix in the sour cream until no white streaks remain. On low speed, add half of the flour mixture, mixing just to incorporate it. Mix in the milk. Add remaining flour mixture until it is incorporated and the batter looks smooth, don't over mix.
Fill cupcake liners with about ⅓ c. batter or ⅔ full. Bake about 15 minutes or until toothpick inserted in the center comes out clean. Everyone's oven is different so test at 15 and if not done bake until they are, no longer than 20 min. Cool 10 minutes on wire rack and turn out to cool completely before frosting and dipping in chocolate.