My mint plant was water logged after a very wet winter in Vancouver, so I used Ketel One Mint & Cumber vodka (20 mL) with plain vodka (25 mL). It worked out well.
Interesting how the Egg-Nog recipe changes when you log into the Diffords web-site. The "Guest" recipe is Cognac & Rum. When you log in, it becomes Courvoisier V.S. & Diplomatico Reserva Rum.