Albondigas (Mexican Meatballs)

SERVINGS: 8

4 dried ancho chiles, seeds removed
1 small white onion, chopped
2 garlic cloves
½ teaspoon ground cumin
2 cups (or more) low-sodium chicken broth
2 tablespoons olive oil, divided
1–2 tablespoons sugar
Kosher salt and freshly ground black pepper
½ cup sour cream
2 tablespoons fresh lime juice
Crumbled Cotija cheese, sliced radishes, toasted shelled pumpkin seeds (pepitas), cilantro sprigs, and lime wedges (for serving)

Preheat broiler. Place poblano chile on a broiler-proof rimmed baking sheet and broil, turning occasionally, until charred in spots and blistered all over, 6–8 minutes. Transfer to a bowl, cover with plastic wrap, and let steam 10 minutes. Remove skin, stem, and seeds; discard. Pulse poblano, onion, garlic, arugula, and cilantro in a food processor until very finely chopped.
Combine tortilla chips and milk in a large bowl; let stand until chips soften, about 5 minutes. Mix in poblano mixture, eggs, and cheese; season with salt and pepper. Gently fold in beef. Form mixture into 1½”-diameter balls (2 Tbsp. each; makes about 40) and chill at least 4 hours.

Place ancho chiles in a small bowl and add boiling water to cover. Let sit until softened, about 15 minutes. Drain chiles. Purée chiles, onion, garlic, cumin, 2 cups broth, 1 Tbsp. oil, and 1 Tbsp. sugar in a blender until smooth, adding more broth by the tablespoonful to thin sauce as needed (should be consistency of whole milk); season chile sauce with salt, pepper, and additional 1 Tbsp. sugar, if sauce is too bitter.
Heat remaining 1 Tbsp. oil in a large nonstick skillet over medium heat. Working in batches, cook meatballs, turning occasionally, until brown all over, 8–10 minutes. Transfer meatballs to a Dutch oven or other large heavy pot and add chile sauce. Bring to a boil, reduce heat, and simmer, turning meatballs halfway through and adding more broth if needed (sauce should come up to about ¾ sides of meatballs), until meatballs are cooked through and sauce is slightly thickened, 15–20 minutes.
Meanwhile, whisk sour cream and lime juice in a small bowl; season with salt.
Serve meatballs with lime sour cream, Cotija cheese, radishes, pumpkin seeds, cilantro, and lime wedges.
Do Ahead: Red chile sauce can be made 3 days ahead. Meatballs can be formed up to 1 day ahead. Cover both separately and chill. Meatballs can be cooked in chile sauce 1 day ahead. Reheat before serving, adding chicken broth or water as needed to thin sauce.