Stir, strain into old fashioned glass with a large cube or sphere. Garnish with an expressed grapefruit swath.
Amargo de Chile is a mole inspired amaro (including 7 different chiles) produced by Chicago-based CH Distillery; as far as I know it's not available outside that market. Sub with a split of Cynar & Ancho Reyes, plus a dash or two of mole bitters.
Part of my ongoing "4 parts, equal parts, stirred" series.