Add cocoa to a large bowl or bowl. Whisk through to remove any lumps.
Cream together butter and cocoa powder until well-combined.
Add sugar and milk to cocoa mixture by adding 1 cup of sugar followed by about a tablespoon of milk. After each addition has been combined, turn mixer onto a high speed for about a minute. Repeat until all sugar and milk have been added.
Add vanilla extract, peppermint essential oil and espresso powder and combine well.
If frosting appears too dry, you can add more milk, a tablespoon at a time until it reaches the right consistency. If it appears to wet and does not hold its form, add more confectioner’s sugar, a tablespoon at a time until it reaches the right consistency.