1 Combine Oil, Vinegar, And Green Onions In A Bowl. Chop Shrimp Into 1/2 Inch Pieces And Add To Oil Mixture. 2 Arrange Leaves Of Lettuce On Individual Plates. Cut Avocados In Half And Remove Pits. Remove Some Of The Avocado Around The Pit Area And Mix In With The Shrimp. With A Spoon, Carefully Scoop Out Avocado Halves From Their Skins In One Piece. Place Avocado Half On Plate With Lettuce. 3 Spoon Shrimp Mixture On To Avocado. Sprinkle With Walnuts And Cilantro (Optional).