Brown Butter Old Fashioned Cocktail

It's traditional to use a sugar cube to make an Old Fashioned, although they vary in size. I've made these with granulated sugar and they come out just fine. Whatever sugar you use, muddle it well with the bitters until it's fully dissolved. I've seen some bartenders add a very small splash of sparkling water to the sugar and bitters mixture to help them meld together. For a slightly different twist, swap out maple syrup for the sugar. I used Bitter Truth Aromatic Bitters for this one (another brand is Fee Brothers), although Angostura bitters are considered the classic, and available in well-stocked supermarkets and online.

Servings cocktail

For the brown butter bourbon

4 ounces (115g, 8 tablespoons) unsalted butter, cubed
2 cups (480ml) bourbon , (or rye)

For the Old Fashioned cocktail

1 1/2 - 2 ounces (45-60ml) brown butter bourbon
2 dashes bitters, (see headnote)
1 teaspoon sugar
1 strip orange zest

To make the brown butter bourbon, melt the butter in a skillet or wide saucepan over medium heat. Continue to cook the butter; it'll sizzle and pop as it cooks, which is the water cooking off.
As the butter cooks, tilt the pan to avoid burning in spots. When the butter quiets down and has turned a nice amber brown color, and smells deliciously nutty, remove from heat and let cool until tepid.
Pour the bourbon (or rye) into a jar, add the brown butter, close the jar and shake a few times to mix the butter with the bourbon. Let stand at room temperature 1-2 hours, shaking it a few times during that period, then refrigerate the bourbon for three days.
After three days, place the jar of bourbon in a saucepan with an inch or two of water in it. Very gently start to warm the bourbon over low heat in the water bath. As soon as the hard disk of butter on top is removable, lift it out (reserve it for another use, see Note at end of recipe). Line a funnel with a few layers of cheesecloth, a paper towel or coffee filter, set over a clean jar. Strain the bourbon into the jar. Chill the bourbon until ready to use.
To make the Old Fashioned cocktail, use a muddler or back of a spoon to mix the bitters with the sugar in a short tumbler or an on the rocks glass, until the sugar is dissolved. Add the bourbon and a large ice cube, or a few ice cubes, and stir for 15 seconds until the cocktail is well-chilled. Twist a strip of orange zest over the glass, spraying the oils into the drink, then drop the zest into the glass and serve.

Notes

Notes: Save the leftover brown butter in the refrigerator. It can be used in recipes such as a crisp topping or in a batch of brownies. It can also be melted and tossed with cooked vegetables, such as carrots, green beans, or Brussels sprouts, or added to the skillet during the last minute of sautéeing fish, scallops, or pork chops.

Large ice cubes are recommended for Old Fashioned cocktails since they melt more slowly than smaller cubes, which dilute the drink. I own these ice cube trays, but you can also freeze water in a metal loaf pan until frozen, then break the rectangle of ice into large chunks, and use one of those. I've written more about that at Basic Cocktail Tools for Setting Up Your Home Bar.

Storage: The brown butter bourbon will keep for a week or two in the refrigerator.