In a non-reactive bowl, marinate the shrimp for 30 minutes in the lemon and grapefruit juice. Season to taste with sea salt. Add the remaining ingredients, mix to combine and refrigerate until ready to serve. Cut avocados in half, remove pit, and peel. Put into blender.
In a small saucepan, saute onion in oil and butter until tender. Add the chicken and garlic. Cook and stir until chicken is lightly browned. Stir in the broth, carrot, peas and basil. Bring to a boil. Reduce heat; cover and simmer for 5 minutes. Add the noodles. Cover and simmer for 8-10 minutes