Add the sugar and water to a small pot. Grate the ginger, peel and all, into the pot (a microplane works best).

Place the pot over high heat, and bring to a boil. Let cook at a rolling boil for 2 minutes.

Remove from the heat, and add vanilla, if using. Set the pot aside, and let the ginger continue to steep for at least 2 hours. Cooled syrup should be stored in a covered jar in the fridge.

To use the syrup, You can either pour the ginger syrup through a sieve each time you want to make soda, or you can strain it all at once after the initial steep. The longer the ginger sits in the syrup, the stronger your ginger flavor will be.

To make ginger ale, fill a glass with ice cubes. Add seltzer, and as much ginger syrup as you like to reach the right level of strength.