Any mushroom you like, fresh or dried, will work here. Ditto for the nuts. I prefer chanterelles and pine nuts. You can make this stuffing a few days in advance, and you can freeze it if you want.
Soak the bread croutons in 1 cup of stock. Chop or tear the chanterelles into medium-sized pieces; leave the small ones whole. Preheat oven to 350°F.
Heat a large sauté pan over medium-high heat for a minute or two. Add the chanterelles and dry sauté them, shaking and stirring them constantly, until they give up their water. Rehydrated dried mushrooms don't need this step, but most fresh ones do.
When most of the mushrooms’ water has cooked away, remove them from the pan and add the bacon. Cook until crispy, then eat a piece. Chop the rest for the stuffing.
Add the salami (if using), onion and celery and toss to combine. Cook for 3 to 4 minutes, stirring often, until the onions are translucent. Sprinkle them with salt. Add the mushrooms back to the mix, along with the thyme and pine nuts and cook for another 2 minutes.
Pour the contents of the sauté pan into a large bowl and mix with the bread croutons and the parsley. Add the other cup of stock, and the beaten eggs, if using. Mix well. Fill a casserole with the dressing, cover and bake 30 minutes. Take the cover off and bake for another 20 to 30 minutes, or until the top browns.
Notes
If you want to make this vegetarian, use butter instead of bacon fat and a vegetable or mushroom stock. If you want to use dried mushrooms, rehydrate them by pouring a few cups of boiling water over them, then strain that water and use it in place of the stock.