Make the fennel simple syrup. Add the fennel seeds, sugar and water to a small saucepan. Bring to a boil, then reduce heat to medium and simmer for 5 minutes, stirring occasionally until sugar is fully dissolved. Once sugar is dissolved and syrup is slightly thickened, turn off heat and allow to cool to room temperature.

train into a jar or airtight container and store in the refrigerator until ready to use. Makes about 1.5 cups, and keeps up to 2 weeks in refrigerator.

Make the cocktail. Add fennel syrup, bourbon, vanilla, bitter and lemon juice to a cocktail shaker or mason jar and shake vigorously. Fill a cocktail glass with ice, and pour over. Top with seltzer water or sparkling mineral water. Garnish with lemon wedge, of desired. Cheers!