Add the softened butter to the bowl of a stand mixer fitted with the paddle attachment. Beat for 2–3 minutes until light and creamy.

Gradually add the powdered sugar, mixing on low until incorporated.

In a small bowl, stir the instant espresso powder into the heavy cream until dissolved.

Add the espresso mixture, vanilla extract and salt to the buttercream.

Beat until smooth and fluffy.

Taste and add additional espresso powder if you'd like a stronger coffee flavor.

If the buttercream is too thick, add heavy cream one teaspoon at a time until you reach your desired consistency.

Use immediately to frost cakes or cupcakes, or store until you're ready to decorate.