Cilantro Lime Sour Cream Ceviche

Lightly blanch shrimp in boiling water for roughly one minute. Transfer to ice water for five minutes, drain and cut shrimp small pieces. Combine citrus juices, add shrimp and marinate for two hours in refrigerator. In a separate bowl, combine onion, tomato, Serrano pepper and cilantro. Add to marinated shrimp and refrigerate for another two hours. Spoon into four individual bowls or cups and finish with cucumber and avocado. Add a 1-oz dollop or drizzle of sour cream to each and serve as-is or with tortilla chips.