Try this lavender collins recipe by Kate Bolt

5 cups gin
2 cups lemon juice
   (I like Italian Volcano brand)
1 cup water
2 cups sugar
3 tablespoons dried lavender
   (available locally at Nature’s Market)
7 cups club soda
Fresh lavender sprig or basil leaves, optional

First, make the lavender syrup: Bring 1 cup water, 2 cups sugar, 3 tablespoons fresh or dried lavender to a boil, stirring with wooden spoon until sugar dissolves. Reduce heat and simmer 5 minutes. Remove from heat and cool for 15 minutes. When cool, strain flowers through a fine mesh sieve twice. Store in refrigerator in a mason jar or use immediately.

Second, mix all ingredients in a large (gallon-sized) container: 5 cups gin, 2 cups lemon juice, and 1 ¾ cups lavender syrup — mixing in 7 cups club soda right before serving. Serve over ice and garnish with fresh sprigs of lavender (if you have a better garden than I do and grow fresh lavender!) or basil leaves.

Serves 20 (in a 10 oz. rocks glass, filled halfway with ice)