Combine the champagne or wine with the lemon verbena and heat to about 180°F (82°C); do not boil. Remove from the heat and set aside to infuse for a minimum of 30 minutes, preferably 1 hour.
Beat the egg yolks and sugar together in a stainless steel bowl until the mixture is light and fluffy. Strain the wine mixture, then whisk it into the egg yolk mixture.