Mexican Shrimp Cocktail

Ingredients

• 1 medium white onion
• 6 large cloves garlic - coarsely chopped
• 2 tablespoons salt - plus more to taste
• 1 tablespoon coarsely ground black pepper
• 1 pound medium shrimp - 31-35 count, peeled, deveined and tails removed except for 4 to go on top as garnish
• 1 1/2 cups Clamato juice - chilled
• 2 tablespoons ketchup
• 3 tablespoons lime juice - or to taste
• Hot sauce - preferably Mexican, to taste
• 1/2 small jicama - peeled and diced (about 1 cup)
• 1/2 large English cucumber - seeded and diced (about 1 cup)
• 1 medium plum tomato - seeded and chopped
• 2 medium avocados - or 1 large avocado, peeled, pitted and chopped
• 1 large jalapeno or serrano pepper - optional, seeded if desired, chopped
• 1 cup chopped cilantro - loosely packed
• Lime wedges - for serving
• Cilantro sprigs - for serving