How Would You Make This?

The shrimp should be last, as they will only take a few min to cook.

saute shallots, or sweat down a bit, depends on the flavor you are going for, I'd add a little garlic and get some color on it, add de-glaze, add in shrooms and a knob of butter, let the shrooms soak it all up, then, I would then add a little more liquid, bring to a simmer, add the shrimp pieces, take off the heat, and start adding in some fresh breadcrumbs for the filler, and let it all come together before incorporating some cheese. Let the stuffing cool. hull the large shrooms, stuff, and broil until the stuffing is golden, and crispy on top. This will also finish cooking off the shrimp pieces throughout the stuffing.

just my $.02

Hmm, I don't think I'd put shrimp in there at all to be honest.  There is nothing worse than overcooked shrimp and if you put them in the stuffing cooked they'll definitely overcook in the oven and if you put them in raw they'll release a lot of water and make the whole thing soggy and overcook too.  I also think the flavor of shrimp is too delicate for the earthiness of the mushrooms and wouldn't pair them together at all, maybe in separate courses.  I have a better recipe that uses sausage if you want it.

Agree with KK. No shrimps here. May be some bacon.

Here's a nice mushroom and feta pie, tho you can use other cheeses:

I have to agree with Miss KK, shrimp as a separate dish.

Also, I like my 'shrooms stuffed with sausage, maybe some hot Italian and some shallots/onions, some garlic. 

Or just a straight up mushroom & bread/cracker stuffing; a sprinkle of parm on top and bake. 

Make it an appetizer kinda' night, shrimp cocktail, a small garden salad, a glass of sparkling wine, oh my, yeah baby!

Had a portabello "appetizer" that coulda been a meal with a salad... at a boardwalk place in Ses Side (Jersey SHore territory).  Grilled portabello, topped with thin slice of grilled chicken, slice of roasted read pepper, topped with melted mozz.  Thinking everything was cooked kinda separately??  Then stacked and under broiler till cheese bubbled.  Could stack with anything you liked... grilled onion maybe... bacon, etc.  COuld have no meat/seafood and be a meal.