Preheat oven to 350° F. Line two standard muffin tins with paper liners and set aside.

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

In a separate medium bowl, whisk together cocoa powder and espresso powder. Add the boiling water and whisk until smooth. Allow mixture to sit until room temperature, then whisk in sour cream, vanilla and peppermint extract. Set aside.

In a the bowl of a stand mixer (or using a hand mixer), combine butter and sugar. Beat on medium-high speed until light and fluffy, about 3 minutes. Add eggs one at a time beating until combined after each addition. Scrape down the sides of the bowl as necessary.

Add one-third of the flour mixture to the large mixing bowl and mix on low speed just until combined. Add half the chocolate mixture and mix until combined. Repeat process, then end with remaining third flour mixture. Use a silicone spatula to scrape the bottoms and sides of the bowl. Mix once more for 10 seconds to ensure all ingredients are incorporated.

Transfer batter to prepared muffin tins and fill each cup two-thirds full (I like to use an ice cream scoop for this step). Bake cupcakes 18 to 22 minutes or until a tooth pick inserted in the center comes out with little to no crumbs. Allow cupcakes to cool for 5 minutes in the pan before transferring them to a wire rack to cool completely.

With the mixer on medium speed, add the vanilla and peppermint extract, then mix until combined. Add heavy cream one Tablespoon at a time until desired consistency is reached. Add a pinch of salt and mix until combined.

Transfer frosting to a piping bag with tip and frost the cooled cupcakes. Garnish with a mini candy cane and sprinkle of crushed peppermint.