Add the bitters, lemon juice, pine syrup and cranberries to a shaker, and muddle the cranberries.
Add the gin or vodka (optional) and ice, and shake until chilled.
Strain into a rocks glass over ice, and top with the lemon-lime soda.
Garnish with 3 cranberries and a sprig of pine.
*Pine syrup: Bring 1 cup of water and 1 cup of sugar to a boil until dissolved. Reduce heat to low, and add a handful of chopped pine needles. Stir and remove from heat, and let sit for 2 hours. Strain and refrigerate. Keeps up to 3 weeks.