1 pound small peeled raw shrimp or cleaned baby squid, or 8 ounces of each 1/2 cup fresh lime juice 1/2 cup minced white onion 2 teaspoons minced garlic 2 teaspoons salt 1/2 teaspoon black pepper 1/4 cup chopped cilantro 1 cup ketchup 2 tablespoons minced green jalapeño chilies, seeds and white ribs removed 1/2 cup diced jicama (optional) 1 avocado, peeled and sliced Fried corn tortillas or tortilla chips Lime wedges and hot sauce for serving. 1. Blanch seafood in plenty of boiling salted water for 2 minutes, then drain and plunge into ice water to stop cooking. Cut squid (if using) into bite-size pieces. In a glass or ceramic bowl, mix seafood, lime juice, onion, garlic, salt and pepper. Refrigerate 30 minutes. 2. Add cilantro, ketchup, jalapeños and jicama (if using) and mix. Refrigerate at least 1 hour, or up to 6 hours. 3. Serve in chilled glasses, topped with avocado slices. At the table, pass tortillas, lime wedges, and hot sauce. Yield: 6 to 8 servings (can be doubled).