Rinse a rocks glass with the Kummel and put the glass in the freezer.
In a chilled mixing glass, add the rye whiskey, aquavit, and bitters. Add ice and stir.
Using a julep strainer, strain the cocktail into the chilled, Kummel-rinsed rocks glass.
Using an aromatizer, mist absinthe over the finished cocktail. Garnish with fennel fronds.