Preheat the oven to 350°F (175°C). Line a standard cupcake pan with paper liners or lightly coat with non-stick cooking spray.

In a small bowl, dissolve the espresso powder in the boiling water. Allow the mixture to cool to room temperature before proceeding.

In a large mixing bowl, using an electric mixer, cream together the butter-flavored shortening and granulated sugar until light and fluffy. Add the eggs, one at a time, beating well after each addition until fully incorporated.

In a separate bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking powder, baking soda, and salt until well blended.

Gradually add the dry ingredients to the creamed mixture, alternating with the cooled espresso mixture. Begin and end with the dry ingredients. Mix until the batter is smooth and homogeneous. Gently fold in the milk chocolate toffee bits.

Spoon the batter into the prepared cupcake liners, filling each approximately three-fourths full. Bake for 20 to 22 minutes, or until a toothpick inserted into the center of a cupcake comes out clean. Remove from the oven and allow the cupcakes to cool in the pan for 10 minutes before transferring them to a wire rack to cool completely.

In a small bowl, combine the vanilla extract with the espresso powder, stirring until the espresso powder is fully dissolved. In the bowl of a stand mixer fitted with the whisk attachment, whip the unsalted butter on medium-high speed for approximately 5 minutes, stopping once to scrape down the sides of the bowl.

Reduce the mixer speed to low and gradually add the powdered sugar, incorporating it a little at a time. Once all of the powdered sugar has been incorporated, scrape down the bowl and increase the mixer speed to medium-high. Whip for an additional 1 to 2 minutes until the frosting becomes light and fluffy. Add the dissolved espresso-vanilla mixture and mix on medium-high speed until fully incorporated, scraping down the sides as necessary.

Once the cupcakes have cooled completely, frost them generously with the espresso buttercream. For garnish, sprinkle the tops with additional toffee bits and chocolate chips, if desired.