Crab and Edamame Sushi Rice

Mike wanted to make a fancy sushi rice type of dish for a potluck at a friend's house.  We were on this Edamame Rice fix from the previous week, so he decided to combine it with a Crab and Shitake Rice recipe.

Mike made edamame rice. He did not follow a recipe, but this is my best guess at his recipe:
Edamame Rice
 4 cups uncooked medium grain rice
1 bag (1 lb bag) shelled, frozen edamame
1/2 bottle aji furikake.

Cook the rice in a rice cooker. Boil some water, throw the frozen edamame into the water and quickly drain the water (you want to do this quickly so you do not overcook the edamame-overcooking results in mushy edamame).  Add the edamame and furikake to the rice.  Transfer mixture to a 9x13" pan.

Mike placed his edamame rice in the fridge (you do not have to refrigerate the edamame rice prior to putting the crab topping on it. we just did this to save time the following day) and the next day I continued the rice-making process.  

I chopped up about 8 oz (1/2 lb) of imitation crab.  

Then added mayonnaise until the imitation crab looked coated (1/2-1cup mayonnaise). I did not have sour cream, so I decided not to add it to the mixture.  Then I spread it over the rice, popped it in the oven on broil for 15-20 minutes and took it out of the oven.  FYI-Not including sour cream is a BAD idea.  While Mike was watching the sushi broil in the oven he yelled, "Oh no, it looks like the mayonnaise is sinking to the bottom of the pan!" I don't think the mayonnaise was dripping to the bottom of the pan, but I do think that adding sour cream would help maintain the crab layer on top of the rice.  

This recipe needs a few more tweaks.  1) I think that the sour cream is necessary in the recipe.  2) The shitake mushrooms or nametake mushrooms should be added to the rice or the crab topping.
I feel that there was something missing in our Crab and Edamame rice. It was missing that extra pizazz to take it from "average" to "great."  It might have been missing an umami flavor that mushrooms could provide.