Buttered Whisky Sour Recipe

Clarify butter

Melt unsalted butter in a small saucepan over low heat until it separates and the milk solids sink. Skim off any foam and pour off the clear butterfat. Allow to cool slightly but remain liquid.

Combine butter and bourbon

In a clean jar, pour 2.5 cups of bourbon. Add the 3 tablespoons of melted clarified butter to the bourbon, seal the jar, and shake vigorously for 20–30 seconds to emulsify.

Freeze and separate

Place the sealed jar in the freezer for 2–3 hours (or until the butterfat solidifies and rises). Once solid, open the jar and pour the bourbon through a fine-mesh strainer lined with cheesecloth into a clean container to remove the solidified butterfat and any trapped solids. Repeat straining if necessary until liquid runs clear. Bottle and refrigerate the butter-washed bourbon. Yield: roughly 2 cups usable bourbon.

To make 2:1 demerara syrup, combine 2 cups demerara sugar with 1 cup water in a small saucepan. Heat gently, stirring until sugar dissolves. Bring to a simmer for 1–2 minutes, then remove from heat and cool. Store in the refrigerator. (If using store-bought syrup, skip.)

Measure

For each cocktail (serves 4 total from these quantities): measure 4 ounces (1/2 cup) butter-washed bourbon, 1.5 ounces (3 tbs) fresh lemon juice, 0.5 ounces (1 tbs) fresh lime juice, 0.5 ounces (1 tbs) demerara syrup, and 1 egg white. (The ingredient list above is scaled to make four servings.)

Dry shake

In a cocktail shaker, combine the measured butter-washed bourbon, lemon juice, lime juice, demerara syrup, and egg white. Seal and shake vigorously without ice for 15–20 seconds to build a froth.

Wet shake

Add a large handful of ice to the shaker and shake again vigorously for 12–15 seconds until the shaker becomes very cold to the touch and the foam is silky.

Double strain & serve

Double-strain the cocktail through a fine-mesh strainer into chilled coupe or rocks glasses (over a large ice sphere if preferred).

Garnish

Break a bourbon biscuit into a small piece and rest it on the rim or float lightly on the foam. Sprinkle 1/8 to 1/4 teaspoon freshly grated lemon zest over the foam and optionally add 2 dashed drops of Angostura bitters onto the foam for aroma. Lightly dust with 1 tsp microplane sugar if desired. Serve immediately.

If you prefer a crumb garnish, pulse remaining bourbon biscuits in a small food processor to coarse crumbs and sprinkle a pinch on each cocktail just before serving.