Combine chicken, garlic, onion, cilantro, salt, peppercorns and allspice with water to cover in a 6 quart heavy pot and bring to a simmer. Simmer, covered, until chicken is just tender, about 50 minutes. Transfer chicken to 13 x 9 inch baking pan. let stock cool.

Pour stock through a fine-mesh sieve into a bow, pressing garlic pulp through sieve; discard solids. Measure 3 1/2 cups stock for sauce and reserve remainder for another use.

Heat a dry 10 inch heavy skillet over moderate heat until hot, then toast pumpkin seeds, stirring constantly, until puffed and beginning to pop, 3 to 5 minutes. Transfer to a plate to cool. Add sesame and cumin seeds, allspice, cloves and peppercorns to skillet and heat, stirring, until fragrant, about 1 minute; transfer to plate. When seeds and spices are cool, grind to a powder, in 4 batches, in coffee/spice grinder.

If using fresh tomatillos. remove husks and rinse with warm water to remove stickiness. Combine fresh tomatillos, serranos, and salted water to cover in a 5 quart heavy pot, bring to a simmer, and simmer for 10 minutes. Using a slotted spoon, transfer tomatillos and serranos to a blender. Or, if using canned tomatillos, drain them and transfer to blender, along with uncooked serranos. Add onion, garlic, 1/4 cup cilantro and salt to blender and puree until completely smooth (use caution).

Put a rack in middle of oven and preheat oven to 350 F.

Heat lard (or oil) in a 5 quart heavy pot. Add tomatillo puree and simmer, stirring frequently, for 10 minutes. Add 3 cups reserved stock and stir in ground pumpkin seed mixture. simmer over moderate heat, stirring frequently, until some greenish oil is visible on surface, 15 to 20 minutes.

Meanwhile, puree poblano with remaining 1/2 cup stock and 1/4 cup cilantro in blender until completely smooth.

Stir poblano puree into sauce and pour over chicken. Back just until chicken is heated through, about 20 minutes. Garnish with pumpkin seeds and cilantro, if desired.

Cook's Notes:

The chicken and stock can be made up to 1 day ahead. Cool completely, uncovered, then refrigerate separately, covered. The extra stock can be frozen for up to 1 month. The sauce can be made, without the poblano puree, up to 1 day ahead. Cool completely, uncovered, then refrigerate, covered. Reheat over moderate heat before proceeding. You can use this as a taco filling by shredding the chicken (discarding bones and skin) and stirring it into the sauce with the poblano puree before baking. Serve with warm tortillas.

Pumpkin Seeds

Green (hulled) pumpkin seeds, or pietas, are an essential part of Chicken in Pumpkin Seed Sauce. They're terrific cocktail nibble as well: toast them in a hot cast-iron skillet until they puff up (stir constantly so they don't get too dark), then drizzle them with a little olive oil and sprinkle them with sea salt. Because the seeds go rancid quickly, buy them at a place with a high turnover. We've had the best luck at natural foods stores. Store them in the freezer.

Makes 8 Servings

Active Time: 1 1/4 hours - Start to Finish: 1 1/2 hours