Add sarsaparilla root, sassafras root bark (or extract if using), wintergreen leaves (or extract if using), star anise, allspice berries, juniper berries (if using), dried orange peel, and a pinch of salt to the saucepan.

Bring the mixture to a gentle simmer over medium heat, stirring occasionally to fully dissolve the sugars. Once simmering, reduce heat to low.

Simmer gently, uncovered, for 10 minutes to extract flavors from the roots and spices. Watch carefully to avoid boiling over.

After 10 minutes, remove the pan from heat and let the mixture steep for an additional 20–30 minutes to intensify flavor. Taste after 20 minutes and steep longer if you want stronger spice/root notes.

Strain the syrup through a fine-mesh sieve or cheesecloth into a clean bowl or jar, pressing on solids to extract as much liquid as possible. Discard solids. Stir in the vanilla extract while the syrup is still warm.

Allow the syrup to cool to room temperature, then refrigerate uncovered until fully chilled (about 1–2 hours) or use immediately if you plan to serve over ice with very cold carbonated water.

Assemble and Serve

For a standard serving ratio, mix 1 part concentrated root beer syrup to 4 parts cold carbonated water. For the quantities above (makes roughly 2 cups syrup), combine about 1/2 cup syrup with 2 cups cold carbonated water for each serving. Adjust to taste (range 1:3 to 1:5).

Fill a tall glass with ice (about 1/2–1 cup ice per serving). Pour the measured syrup over the ice.

Slowly add the cold carbonated water down the side of the glass to preserve carbonation and produce a foamy head. Stir gently once or twice to combine.

Garnish with a thin orange slice or a sprig of mint if desired and serve immediately.

Store unused syrup covered in the refrigerator for up to 2 weeks. Re-stir or gently shake before using if separation occurs.