Add the fennel vodka, orange juice and bitters to a cocktail shaker filled with ice. Place the top on the shaker and shake for 1 minute. Strain into a chilled coupe. Serve garnished with a fennel frond floating on top.
In a Mason jar, combine the vodka, fennel seeds and fennel tops. Cover and refrigerate for 1 week. Strain, then store in the refrigerator.