Have you ever had a whiskey sour with egg white and bitters? Then you’ve had a Boston Sour! You may not have known it at the time, especially as many bartenders today favor the inclusion of an egg white in Whiskey Sours, often without using the cocktail's proper name.
The Whiskey Sour is one of the most classic cocktails, but making a Whiskey Sour with egg, aka the Boston Sour, will delight both your tastebuds and guests. The egg white adds a silky-smooth feel, creamy taste and frothy foam - what’s not to love?
History of the Boston Sour
The Boston Sour is part of the sour family of cocktails. These combine a base spirit, a sour element (typically citrus) and a sweetener to make cocktails such as daiquiris, sidecars and margaritas. You can read more about this family of cocktails on one of our previous posts, where we explain how to riff on the sour cocktail, and give tips on how to properly make sours of all kinds.
The basic recipe for a Whiskey Sour was first recorded in 1862 in The Bartender’s Guide, but it had been around for many decades prior. In the 19th century, professional sailors making the trek from Europe to North America would often suffer from scurvy, which results from a lack of vitamin C (ascorbic acid) in the diet. Vice Admiral Edward Vernon, a British naval officer, came up with the genius idea to mix a few of the ingredients on board together to help the sailors cope with this ugly illness. In its earliest form, the Whiskey Sour was lemons or limes mixed with liquors such as gin, rum, brandy or whiskey. Nothing like a bit of spirit to raise the sailor's spirits, and ensure they got their vitamins! As the sailors made their way to North America, so did this cocktail recipe.
The Boston Sour, distinguished from the Whiskey sour with the addition of egg, first appeared in recipes in William Schmidt’s 1892 The Flowing Bowl. It’s believed that the egg white helped smooth the harsh, bootleg alcohol used in Whiskey Sours during prohibition, which is why it was first introduced.
How to Make the Boston Sour
As mentioned above, a sour cocktail is defined as a spirit, a sour and a sweet. For a Whiskey Sour this distills down (pun intended!) to whiskey + lemon juice + simple syrup. But of course, the Boston Sour is a Whiskey Sour plus egg.
It’s understandable if you’re nervous about serving raw eggs to your guests, but as long as you are careful, there should be no issue. When cracking the egg, try not to touch the egg white to the outer shell. Most commercially sold eggs are washed and pasteurized, and pose little health risk. If you're extra-concerned, you can purchase pasteurized egg whites that have already been separated.
We always recommend using a jigger for measurements when making any cocktail, and the Napier Stepped Jigger does a great job of being supremely accurate and beautiful to boot!
Another key component for the Boston Sour is dry-shaking the cocktail before adding ice. This is a critical step to achieve perfect foam! While simple to make, the Boston Sour comes together nicely for a beautiful presentation with its white frothy top with speckles of bitters.
Boston Sour Cocktail Recipe
- 2 oz whiskey (we recommend Bourbon or Rye)
- ¾ oz fresh lemon juice
- ¾ oz simple syrup (1 part sugar to 1 part water)
- 1 fresh egg white
- Aromatic bitters (we use Angostura) and/or brandied cherry (we recommend Luxardo Maraschino Cherries) for garnish
Add the whiskey, lemon, simple syrup and egg white to a cocktail shaker. Dry shake the Boston Sour cocktail for 5 - 10 seconds without ice to emulsify and froth the egg white. Add ice to your cocktail shaker and shake for about 5 seconds until the outside is cold and starting to frost. Strain the Boston Sour into a chilled cocktail class. If your cocktail strainer restrains the whipped egg white foam, use a bar spoon to add a bit more to the glass. Garnish your Boston Sour with a few dashes of aromatic bitters and a brandied cherry (if desired).
Variations and Substitutes
One of the best parts about a simple cocktail, such as this Whiskey Sour with Egg, is that you can adjust the flavor to your tastebuds rather easily. Do this by playing with the measurements and proportions of your sour and sweet ingredients. If you like a drink that’s less sweet, start with ¼ oz of simple syrup and test from there what works for you. If you find the Boston Sour is too sour, add more simple syrup.
Additionally, you can experiment with different sweeteners such as honey syrup or maple syrup. To make honey syrup, combine 1 cup or honey and ⅓ cup of water in a saucepan over medium heat. Stir occasionally until all the ingredients have integrated. Both honey syrup and maple syrup pair well with whiskey and would be a great addition to any Autumn party.
Thankfully, the Boston Sour has come a long way since its origin for sailors on the Atlantic Ocean. While it maintains its simple recipe, the flavors are bold yet light with a silky-smooth finish.
Rachel Eva & Shawn Michael