Combine muddled kumquats, agave nectar, and water in a small saucepan. Warm gently over low heat (do not boil) for 5–7 minutes, stirring and pressing fruit to extract flavor.

Remove from heat and let cool slightly, then strain through a fine mesh sieve or cheesecloth into a jar, pressing solids to extract syrup. Discard solids.

Stir in the optional lemon juice if using to brighten the syrup. Chill syrup before using. Yields roughly 6 oz; store in refrigerator up to 2 weeks.

Cocktail Assembly

If using the rice wash: add 0.25 oz clarified rice water to an Old Fashioned glass and swirl to coat the inside, then discard excess (this imparts a subtle rice-washed character).

In a mixing glass filled with ice, combine 2 oz añejo tequila and 0.5 oz kumquat–agave syrup.

Add 2 dashes Angostura bitters and 1 dash orange bitters to the mixing glass.

Stir the mixture briskly for 20–30 seconds until well chilled and slightly diluted (smooth, glossy texture).

Strain over a single large ice cube or sphere into the prepared Old Fashioned glass.

Express oils from a kumquat wheel or twist over the drink, then drop the fruit into the glass as garnish.

Serve immediately.