Combine all ingredients (except ginger beer and garnish) in a cocktail shaker filled with ice. Shake for 15 seconds and pour contents of the cocktail shaker into a copper mug. Top with ginger beer and garnish with a mint sprig, four black peppercorns and a lime wheel.Peppercorn Syrup: pour equal parts sugar and water into a saucepan, heat ingredients at medium high until sugar has dissolved. Remove from heat and add ¼ cup of whole black peppercorns into the syrup, seal in an airtight container and allow to chill. Remove the black peppercorns once the syrup has fully chilled and keep refrigerated.