Instructions: To simmer chicken: Bring 6 cups water and 1/2 teaspoon salt to a boil in a large saucepan with diced onion. Add chicken breasts, skim off any grayish foam that rises during the first minute of simmering, partially cover and simmer over medium heat for about 12 minutes, until breasts are barely done. If there is time, let chicken cool in broth. Remove chicken; strain broth, then spoon off all the fat that rises to top.

For pumpkin seeds: Heat medium skillet over medium-low for several minutes, then pour in pumpkin seeds in single layer. When first one pops, stir them constantly for 4 to 5 minutes, until all have toasted and popped. Cool completely. In batches, pulverize seeds in a spice grinder (or in a blender fitted with a miniblend container). Sift through medium-mesh sieve, then stir in 1 cup of broth from chicken.

For vegetables and spices: If using fresh tomatillos, simmer them with whole chiles in salted water to cover until tender, 10-15 minutes; drain and place in blender or food processor. Simply drain canned tomatillos and place in blender or food processor with raw chiles.

Tear lettuce leaves into rough pieces and add to tomatillos along with onion, garlic and fresh cilantro. Pulverize spices in a mortar or a spice grinder, add to blender, then process until smooth.

Heat lard or oil in large saucepan over medium. When hot, add pumpkin seed-broth mixture and stir constantly as it thickens and darkens, 4-5 minutes.

Add vegetable puree and stir a few minutes longer, until very thick.

Stir in 2 cups chicken broth, reduce heat to medium-low and simmer, partially covered, for about 30 minutes. For a smooth sauce, scrape into a blender, blend until smooth, then return to saucepan. Season with salt and, if necessary, thin to a light consistency with a little broth.

Just before serving, add chicken to simmering sauce. When heated through, remove breasts to a warm serving platter, spoon sauce over them and decorate with sprigs of cilantro and radish roses.

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