Heat oil in a large saucepan to 350°F. Fry tortilla rounds in small batches until crisp and brown. Remove to a paper towel lined plate to drain. Reserve.
To make the guacamole, remove the pit and peel from the avocado. Mash in mortar and pestle or with the back of a spoon in a bowl. Add the onion, jalapeño, tomatillo and cilantro and the juice from the lime. Stir to combine and season with salt to taste. Reserve.
To make the salsa, heat a large skillet over high heat, char the tomatillos lightly on all sides. Add the chilies and garlic and lightly toast without burning. Add a cup of water. Bring to a simmer. Cook for 2 minutes. Remove from the heat and allow the chilies to soften. Add contents of the skillet to a blender jar and puree until smooth. Reserve.
To serve, place a small spoonful of the guacamole on each tostada, top with a spoonful of the crab and finish with a little of the salsa.
Enjoy with a glass of Cakebread Cellars Sauvignon Blanc