Start by adding aquavit and elderflower liqueur into a shaker.
Cut thin slices of cucumber and add them to the shaker. For example, use a Y-peeler for this.
Next, add the white wine and sugar syrup to the shaker.
Finally, add the egg white, lemon juice, and dill.
Put the lid on the shaker and "dry-shake" it - that is, shake it without ice. This is always done when using egg whites, as the cold will ensure that the egg whites cannot mix with the other ingredients.
Take off the lid, fill the shaker with ice cubes, put the lid back on, and shake well.
Put ice cubes in a glass and pour your cocktail through a strainer before it goes into the glass. This way, you won't get any lumps from the dill or cucumbers.
Cut another thin slice from the cucumber for garnish. Roll it up on a toothpick and place it on top of the glass. Optionally, garnish with a bit of dill on top.
Cheers.