It is a tasty drink, and one I was surprised by. The sweetness of the bourbon works well with the fruitiness of the elderflower. I would also recommend an orange twist as a garnish. The original recipe by Mr. Difford called for orange bitters, so you may also try that.
Bourbon & Elder
0.75oz elderflower liqueur
1 dash angostura bitters
garnish: lemon twist
Stir with ice and strain into chilled old-fashioned glass. Add lemon twist.