Caldo de Camaron (Shrimp Soup)

1. For shrimp stock: In a saucepan combine reserved shrimp shells, 1/4 onion, two of the garlic cloves, the bay leaf, and 5 cups water. Bring to boiling over medium-high. Reduce heat; simmer 8 minutes. Remove from heat and strain.

2. Meanwhile, place tomatoes and the remaining 1/4 onion and two garlic cloves on a hot griddle or in a cast-iron skillet over medium, turning occasionally for an even roast, about 8 minutes.* (Remove garlic promptly as it browns. If it burns, it will be bitter.)

3. Place roasted tomatoes, onion, garlic, and the chipotle in a blender or food processor. Cover; blend until smooth.

4. In a medium saucepan heat 2 Tbsp. olive oil over medium. Add carrots; cook 2 minutes. Stir in potatoes; cook 6 minutes, stirring often.

5. Strain tomato mixture through a fine-mesh strainer into the saucepan with the carrots and potatoes. Bring to boiling. Reduce heat and simmer 10 minutes. Add shrimp stock and shrimp. Gently simmer 5 to 7 minutes or until shrimp are a light pink-orange color but still look firm. (Don't overcook or shrimp will have a rubbery texture.) Add the epazote and cook 2 more minutes, then season with kosher salt and black pepper. Serve immediately with tortillas and lime wedges. Serves 6.

Tips

"If you can't find fresh epazote, you can use dried epazote or fresh cilantro," Mely Martínez says. Substitute 1/2 tsp. dried epazote or 3 to 4 Tbsp. cilantro.You can also roast the tomatoes, onion, and garlic in the oven: Roast 20 minutes at 425°F on a parchment paper-lined baking sheet.