Shrimp Tostadas with Lime-Cilantro Sauce

Ingredients

• 1-1/2 pounds peeled and deveined cooked shrimp (26-30 per pound), coarsely chopped
• 1-1/2 cups chopped, peeled English cucumber
• 8 radishes, thinly sliced
• 4 plum tomatoes, chopped
• 4 green onions, chopped
• 2 jalapeno peppers, seeded and minced
• 2 tablespoons minced fresh cilantro
• 2 tablespoons lime juice
• 3 garlic cloves, minced
• 1 teaspoon salt
• 1/4 teaspoon pepper
• 1 medium ripe avocado, peeled and cubed
• SAUCE:
• 1 cup sour cream
• 2 tablespoons minced fresh cilantro
• 1 teaspoon grated lime zest
• 1 tablespoon lime juice
• 1/4 teaspoon salt
• 1/4 teaspoon ground cumin
• 1/8 teaspoon pepper
• ASSEMBLY:
• 10 tostada shells