For tomatillo salsa:
4 pasillas de Oaxaca (dried smoked chiles), wiped clean
1 pound fresh tomatillos, husked and rinsed, then quartered
1 cup packed cilantro sprigs
2 garlic cloves
1 tablespoon packed dark brown sugar
1 teaspoon molasses (not blackstrap)
1/2 teaspoon ground cumin
1/3 cup vegetable oil
For steaks and tomatillo salad:
1/4 cup vegetable oil, divided
3/4 teaspoon ground cumin
1 3/4 pounds skirt steak, halved
1/2 pound fresh tomatillos, husked and rinsed
1 cup cilantro leaves
2 teaspoons finely chopped shallot
2 teaspoons fresh lime juice
Slit chiles lengthwise, then stem and seed. Heat a dry heavy skillet (not nonstick) over medium heat until hot, then toast chiles, opened flat, turning and pressing with tongs, until more pliable and slightly changed in color, about 1 minute. Cover chiles with hot water in a bowl and soak until softened, about 20 minutes, then drain.
Purée chiles, tomatillos, cilantro, garlic, brown sugar, molasses, cumin, and 1 teaspoon salt in a blender until smooth, about 1 minute.
Heat oil in a 10-inch heavy skillet over medium-high heat until it shimmers, then cook salsa (it will spatter), stirring occasionally, until slightly thicker, 5 to 8 minutes.
Prepare a grill for direct-heat cooking over hot charcoal (high heat for gas).
Whisk together 2 tablespoons oil, cumin, 1 1/2 teaspoons salt, and 1 tsp pepper, then coat steaks.
Oil grill rack, then grill steaks, covered only if using a gas grill, turning once, until grill marks appear, 4 to 6 minutes total for medium-rare. Let steaks rest on a cutting board, loosely covered with foil, 10 minutes.
Make salad while steaks rest:
Thinly slice tomatillos and toss with cilantro, shallot, lime juice, remaining 2 tablespoons oil, and salt and pepper to taste.
Cut steaks into serving pieces and top with salsa and salad.
Steaks can be cooked in a hot oiled 2-burner grill pan over medium-high heat, 4 to 10 minutes for medium-rare.
Salsa (not salad) can be made 1 day ahead and chilled. Rewarm before serving.