I actually had some dried shiitake mushrooms I reconstituted for this recipe, along with some cremini. Lately I've been buying mushrooms from the bulk bins so I can choose the 'shrooms I want and not wind up with a carton of bad looking ones. Sometimes, this also means skipping the variety I want in favor of what's available.
I hollowed out three sweet onions. I could have used some direction from the cookbook, as this was a really difficult activity! I cut circles straight down with my knife, but that was only a partial solution because I wanted to scoop out onion layers spreading out in an ellipse, not just a circle. I did a good enough job, although I was worried the knife might slip and cut me. I didn't hurt myself, although I did get onion all over my hands.
Chop the onion pieces along with mushrooms and a few garlic cloves. I figure for this the measurements are pretty arbitrary and are mostly determined by the size of your onions. I had too much stuffing mix and wish I'd used less onion, or less breadcrumbs. Or less of both. Which brings me to the rest of the ingredients: some hoisin, sesame oil, and salt.
Stuff each of the onions, place in the slow cooker, and add a cup of water and more hoisin. I actually used the water I used to rehydrate those mushrooms.
I served with quinoa, just cooked plain, and that provided a great mellow flavor to balance my over-sweetened stuffed onion.