Pre-Columbian Mexico. The tomatillo (Physalis philadelphica) is native to Mexico and Central America and has been cultivated for at least 3,000 years.
Salsa verde is built from tomatillos (Physalis philadelphica — not green tomatoes, an entirely different plant) combined with fresh green chiles (serrano or jalapeño), white onion, garlic, and cilantro. The tomatillos unique flavour — tart, vegetal, with notes of gooseberry, citrus, and apple — is the defining element. Three preparation methods: raw (raw blended tomatillos — the most tart and herbaceous), boiled (simmered tomatillos produce a more mellow, rounded flavour), and charred/roasted (dry-roasted on a comal or broiled under a salamander — produces a smoky, caramelised depth). The raw preparation is used for guacamole verde (tomatillo guacamole) and aqua fresca applications; the boiled preparation is the standard for enchiladas verdes and chiles en salsa verde; the charred preparation is used for tacos, carnitas, and deep-flavoured applications. Tomatillos must be husked and washed — the outer papery husk is removed and the sticky residue on the fruit rinsed under cold water; this residue is bitter and the washing step is essential.
Raw salsa verde is bracingly tart and herbaceous; boiled salsa verde is rounded and vegetally sweet; charred salsa verde is complex with smoke and caramel notes that balance the tomatillos natural acidity.
Always wash tomatillos after husking — the sticky residue is bitter For boiled salsa verde: simmer until the tomatillos have softened and turned from bright green to olive-drab — this colour change indicates full cooking Serrano chiles produce a brighter, more piercing heat than jalapeños; adjust quantity according to heat preference Blend while hot for a smoother sauce; allow to cool slightly before adding cilantro to prevent enzyme-driven colour loss
A large avocado leaf (Persea americana, toasted briefly on the comal) added to boiled salsa verde creates a remarkable anise-licorice depth; this is a Oaxacan technique For the brightest green colour in blended salsa verde, blend with a handful of spinach or flat-leaf parsley — the chlorophyll maintains colour longer La Costeña canned tomatillos are an acceptable substitute when fresh are unavailable; drain and rinse thoroughly
Using green tomatoes as a tomatillo substitute — the flavour profiles are entirely different; tomatillos have a unique tartness from malic and citric acid that green tomatoes lack Adding cilantro to boiling-hot salsa — the chlorophyll degrades immediately and the salsa turns khaki-coloured Not washing the sticky residue — introduces noticeable bitterness
Diana Kennedy, The Art of Mexican Cooking; Rick Bayless, Authentic Mexican; Roberto Santibañez, Truly Mexican