Step 1In a small bowl, mix together the red onion and cucumber. Carefully fold in the avocado, taking care not to crush it.
Step 2Add the oil. Season with lemon juice and salt and pepper to taste.
Step 1In a large pot, add the water, carrots, onions, leek and fennel. Make a bouquet garni by tying together the leek leaves, parsley sprigs, thyme sprigs and bay leaf and add to the pot. Add the peppercorns and bring the mixture to a boil.
Step 2Reduce to a simmer and add the white wine and vinegar. Squeeze in the lemon juice and add the rind to the pot too. Simmer 20 minutes.
Step 3Add the shrimp to the simmering pot and cook 1 minute. Remove the pot from the heat. Place the shrimp in a large glass bowl and cool to room temperature. Cover tightly and refrigerate until chilled or for up to a day.
Step 4Peel the shrimp, removing the shells but keeping the tail tips intact. Dry the shrimp on paper towels. Cut each shrimp lengthwise in half down the back, and use a paring knife to remove the vein that runs the length of the shrimp.
Step 5Spear each shrimp half on the tip of a fork. Arrange the forks on a platter and place a spoonful of salsa on the fork behind each shrimp.