Dillon created this soda with Emily Crawford, another Seattle chef.
Place lovage leaves and lemon juice in a large nonreactive bowl and gently smash with the end of a thick wooden spoon or wooden rolling pin until leaves begin to bruise. Add sugar and salt and continue muddling to release the herb's essential oils, about 30 seconds.
Bring the water to a boil. Stir lovage mixture into boiling water, remove from heat, and let infuse 20 minutes.
Pour syrup through a fine sieve into a bowl; discard solids, then refrigerate until cold, about 30 minutes. Fill glasses with ice, add 3 tablespoons syrup to each, and top off each with 3/4 cup seltzer. Garnish drinks with lovage straws and serve immediately.
Lovage syrup can be stored in refrigerator up to 1 week.