Put the ice and gin in a tumbler or in a large glass. Rub the lemon peel on the edge of the glass (being careful to only rub the outer part, the one rich in essential oils and not the very bitter white part). Then, place it in the tumbler. Allow 5 to 10 seconds to pass in order to release the aromas of the gin and lemon. Finally add the tonic water, a couple of grains of black pepper and gently mix the gin and tonic with a long teaspoon. Garnish with a few mint leaves and enjoy.