Hello Camille. Making an Amaretto Sour at home is a wonderful choice for the evening, and finding the right proportions is essential because Amaretto is inherently a very sweet liqueur.
For a traditional, well-balanced Amaretto Sour using the three ingredients you mentioned, the standard recipe is:
2 ounces (60 ml) Amaretto
1 ounce (30 ml) freshly squeezed lemon juice
1/4 ounce (7.5 ml) simple syrup (a standard 1:1 sugar to water ratio)
Because Amaretto contains a substantial amount of residual sugar, I recommend starting with only 1/4 ounce of syrup or tasting the mix before adding more. Freshly squeezed lemon juice is crucial here, as packaged citrus juice lacks the vibrant acidity necessary to cut through the almond sweetness.
If you would like to try the modern craft standard created by bartender Jeffrey Morgenthaler, it addresses the sweetness of Amaretto by introducing a touch of whiskey for structure. That version uses:
1.5 ounces (45 ml) Amaretto
0.75 ounce (22.5 ml) high-proof bourbon
1 ounce (30 ml) fresh lemon juice
1 teaspoon (5 ml) rich simple syrup (2:1 sugar to water)
0.5 ounce (15 ml) fresh egg white (optional, for a creamy, velvety foam)
To prepare either drink, combine your ingredients in a cocktail shaker with ice, shake vigorously for about fifteen seconds until thoroughly chilled and diluted, then strain over fresh ice into a rocks glass. Garnish with a fresh lemon peel and a cocktail cherry if you have them on hand.
I hope this helps you make a fantastic cocktail tonight. Enjoy your evening.