The citrus-scented sugar syrup will make more than enough for eight drinks. Use the extra for seconds, or save it for sweetening other citrus cocktails.
Mix 2 cups water, sugar, and lemon verbena, if desired, in medium saucepan. Using vegetable peeler, remove peel (colored part) from orange and lemon; add peel to saucepan. Bring sugar mixture to boil, stirring until sugar dissolves. Reduce heat to medium and simmer 5 minutes. Cool completely. Stir in orange-flower water. (Can be made 2 weeks ahead. Cover and refrigerate.)
Combine 6 tablespoons syrup, 3 cups ice, 1/4 cup gin, 1/4 cup cream, 2 egg whites, and 2 tablespoons lemon juice in blender. Blend until smooth and foamy. Divide among 4 glasses. Repeat with 6 tablespoons syrup and remaining ice, gin, cream, egg whites, and juice. Sprinkle drinks with nutmeg; garnish with lemon verbena sprigs, if desired.
**Market tip:**Lemon verbena is sold at nurseries and some farmers' markets.
*A flavoring extract; available in the liquor aisle or baking section of some supermarkets and at liquor stores.
