II
The Method
1
Place the chicken or pork pieces in a pot with enough water or light stock to cover. Bring to a gentle simmer and cook until the meat is just tender and the broth runs clear. Remove the meat and reserve the broth separately; the broth should be pale and clean-flavoured.
2
Set a dry skillet over medium heat. Add the pepitoria in a single layer and toast, stirring constantly, until the seeds are lightly golden and begin to pop. Remove immediately from the heat. The seeds must be evenly coloured — pale gold, not brown — and emit a dry, nutty fragrance. Untoasted seeds will produce a flat, grassy base that no subsequent step can correct.
3
In the same dry skillet, char the miltomates and fresh green chiles over high heat, turning until their skins blister and blacken in places. The miltomates will soften and collapse slightly; the aroma is sharp and smoky. Transfer to a blender.
4
Add the toasted pepitoria to the blender with the charred miltomates and chiles. Add a ladle of the reserved meat broth and blend to a smooth, cohesive paste. The colour at this stage will be pale olive-green. Pass through a sieve if a finer texture is required.
5
Pour the blended base into a wide, deep pan over medium heat. Stir in enough reserved broth to achieve a flowing sauce — not a paste. Add the chayote wedges and cook for 20 minutes, until they yield to the tip of a knife but retain their shape. Add the green beans and cook a further 5 minutes. The sauce should coat a spoon lightly; it must carry visible vegetables and must not be allowed to over-thicken.
6
This is where the dish lives or dies: remove the pan from the heat entirely. Stir in the cilantro, hierba santa, and mint. Return the cooked meat to the pan. The residual heat is sufficient to wilt the herbs and warm the meat through. The sauce must remain vivid, bright green — if the pan is left on the flame even briefly after this point, the herbs will oxidise and the colour will fall to army-drab, a fault that cannot be reversed.
7
Taste for salt and adjust. Serve immediately; the pepián verde should pour freely over the meat and vegetables, with the green colour still vivid and the aroma sharp with tomatillo and fresh herb.