Ingredients

• 10 poblano chiles
• 2 ears of corn, husked
• 2 tablespoons vegetable oil
• 1 large white onion, thinly sliced
• 1 teaspoon kosher salt, plus more to taste
• 1/4 cup crema (Mexican salted cream) or sour cream
• 16 small corn tortillas or store-bought crispy tostada shells
• Vegetable oil (for frying; if needed)
• Kosher salt (if needed)
• 1 1/2 cups Creamy Black Bean Spread (optional)
• Shredded iceberg lettuce, thinly sliced white onion, queso fresco, cilantro leaves with tender stems (for serving)
• A candy or deep-fry thermometer

Instructions

1. Preheat broiler. Arrange chiles in a single layer on a rimmed baking sheet. Broil, turning once, until blackened in spots, about 15 minutes. Transfer chiles to a large bowl, cover with plastic wrap, and let steam 15 minutes. Peel, seed, devein, and thinly slice chiles lengthwise.
2. Meanwhile, prepare a grill or grill pan for medium-high heat. Grill corn, turning occasionally, until kernels are tender and charred in spots, 15–20 minutes. Let cool, then cut kernels off cob.
3. Heat oil in a large skillet over medium. Add onion and cook, stirring occasionally, until light golden and tender, 10–12 minutes. Reduce heat to low, add chiles, corn, and 1 tsp. salt, and cook, stirring occasionally, until warmed through, about 2 minutes. Stir in crema and just heat through (do not bring to boil)-vegetables should be just coated; add more crema if needed. Season with salt.
4. Assemble the tostadas: If frying tortillas, fit a large skillet with candy or deep-fry thermometer; pour in oil to measure 1". Heat over medium-high until thermometer registers 375°F. Fry tortillas in batches until crispy, turning every 30 seconds, about 2 minutes total. Drain on paper towel-lined baking sheets and season with salt. Spread 1 Tbsp. Creamy Black Bean Spread, if using, on a tostada shell. Top with 1/4 cup rajas, then lettuce, onion, queso fresco, and cilantro. Repeat with remaining tostada shells. Serve at room temperature.
5. If frying tortillas, fit a large skillet with candy or deep-fry thermometer; pour in oil to measure 1". Heat over medium-high until thermometer registers 375°F. Fry tortillas in batches until crispy, turning every 30 seconds, about 2 minutes total. Drain on paper towel-lined baking sheets and season with salt.
6. Spread 1 Tbsp. Creamy Black Bean Spread, if using, on a tostada shell. Top with 1/4 cup rajas, then lettuce, onion, queso fresco, and cilantro. Repeat with remaining tostada shells. Serve at room temperature.
7. Do Ahead Rajas can be chilled for up to 1 day. Reheat and let cool to room temperature before serving.
8. Rajas can be chilled for up to 1 day. Reheat and let cool to room temperature before serving.