Pumpkin Sour

First you need to make the spiced pumpkin syrup. In a saucepan, add a cup of brown sugar, a cup of water, half a cup of pumpkin purée, and a teaspoon each of nutmeg, ginger, allspice and cinnamon. Over medium heat until slightly thickened. Remove from the heat and place a vanilla pod into the syrup and chill overnight. Strain through a cheesecloth and store in a covered container, in a fridge, for up to one week.// Combine the bourbon, lemon juice, egg whites and pumpkin syrup in a cocktail shaker with ice. Shake well then strain into a rocks-filled rocks glass. Garnish with ground nutmeg, a cherry and the bitters.