Chop the avocado flesh and put it into a bowl. Add the smoked fish and the roe. Add salt, olive oil and Sherry vinegar, mix and set aside. Wash the lettuce and escarole, drain well and set aside. Prepare a trout roe vinaigrette by whisking olive oil, sherry vinegar, balsamic vinegar, salt and trout roe. Place a cake ring on a serving plate, pour in the avocado mixture first, about 2cm high, spreading it and leaving a hole in the center. Fill the rest of the ring with mixed lettuce and escarole adding the trout roe vinaigrette on top, then remove cake ring.