Combine the flour, baking powder and salt in a large bowl. Reserve.
In the bowl of a stand mixer combine the butter and sugar. Using the paddle attachment beat the butter and sugar together until they are light and fluffy. Turn the mixer off and scrape down the sides of the bowl.
Beat in the eggs, 1 at a time. Slowly add the vanilla, milk and sour cream. Scrape down the sides of the bowl, as needed. With the mixer on medium speed, gradually mix in the flour.
Line a muffin tin with paper muffin cups. Fill the muffin cups about 2/3 of the way, dividing the batter evenly among the lined cups.
Put in the preheated oven and bake for about 20 minutes. Check about halfway through the baking process to make sure everything is going along great and also rotate the muffin tin.
The cupcakes are done when a toothpick comes out clean when inserted into the middle of a cake. Remove from the oven and let cool completely on a wire rack, then frost and decorate.
Put the chocolate chips in a heat-proof bowl. Put 1-inch of water in a saucepan and put the bowl of chips on top of the pan. Bring the water to a boil over medium heat. Gently stir the chips around until they are 3/4 of the way melted. Remove the bowl from the saucepan and stir occasionally until all the chips have melted.
In the bowl of a stand mixer with the paddle attachment, beat the butter until light and fluffy. Scrape down the sides and add the powdered sugar, vanilla and salt. Beat on low speed until the mixture is combined. Then turn the mixer speed to medium-high and beat for 30 seconds. Turn down the mixer and add the chocolate gradually. Turn up the mixer again and beat until the chocolate is completely incorporated and the frosting is light and fluffy.