Preheat oven to 350°F. Line 24 cupcake tins with liners and set aside.

In a medium bowl, whisk together the flour, baking powder, and baking soda. Set aside.

In the bowl of your stand mixer, beat butter on medium speed until light and fluffy.

Reduce mixer speed to low, then add the sugar and beat until smooth, scraping the bowl as needed.

Add the eggs, one at a time, beating after each until blended. Add the vanilla extract until blended.

With the mixer speed on low, alternately add flour mixture and sour cream to the batter, starting and ending with the flour mixture. Scrape sides of bowl as needed. Beat until smooth.

Fill prepared cupcake tins 3/4 full and bake for about 20 minutes, until tops spring back when lightly touched in the center. Let cupcakes cool completely on wire racks.

In a large CLEAN (grease free) metal mixing bowl, whisk egg whites and sugar over a pot of simmering water.

Continue simmering the water and whisking the mixture until it forms a syrup – when you rub a bit between your fingers you should not feel granules of sugar.

Once you have a thick, smooth syrup, remove from heat and place bowl on your mixer. Using the whisk attachment, beat on low speed for 5 minutes.

Add your vanilla extract and increase speed to high and beat for five minutes more. The frosting should form stiff peaks.

Using a large piping tip, pipe frosting high on cupcakes. Place in the freezer for about 15 minutes while you prepare the butterscotch shell.

In a microwave safe bowl, heat butterscotch chips and 5 Tablespoons of shortening in the microwave, stirring every 20 seconds until smooth.

Stir remaining shortening until smooth and thin enough to dip cupcakes in – if too thick, add shortening, 1 Tablespoon at a time until desired consistency is reached.

Remove cupcakes from freezer and dip frosting in the dip, letting excess drip off. Let butterscotch firm, then serve.