Step 1 Heat the cream, milk and lemon verbena in a saucepan until the temperature reaches 170 degrees, and the mixture is just starting to simmer. Remove from heat, cover and steep for 30 minutes. Strain out the lemon verbena.
Step 2 Using an electric mixer, whisk the yolks with half of the sugar until the mixture is pale in color and a ribbon consistency.
Step 3Add the remaining sugar to the saucepan with the cream mixture and bring it back to a simmer, cooking until the sugar dissolves.
Step 4Slowly whisk in a third of the hot sugar-cream mixture into the yolks to temper, stirring constantly. Pour it all back into the pan and continue to stir until the mixture coats the back of the spoon. Pour into a bowl and set over a bowl of ice water until cool.
Step 5Refrigerate overnight. Freeze in an ice cream maker the next day according to the maker's instructions. Makes a generous quart.