Mix in the order: cacao, menthe, Whiskey, Milk. Try to keep the layers separate. Float on the back of a spoon, tilt the glass and pour very gently, etc. I suggest tilting the glass. When you tilt the glass you can, when pouring the Cream/Milk, rotate the glass causing the Cream to swirl down through the other layers which looks good. Serve in an aperitif glass.