Cut the mushrooms in half, then slice lengthwise. Since camping pans are usually not very large, you may want to work in batches and start cooking the first half while you slice up the rest.
Melt 1 tablespoon of butter in a pan and add the mushrooms. Cook until they have released all the water, about 6 minutes, then add salt to taste. Remove from the pan, add another tablespoon of butter and cook the second batch. Stir in some salt and remove also the second batch from the pan.
Push out the salsiccia from its natural casing and form small meatballs. Add the salsiccia meatballs to the pan. If the pan is not non-stick, you may want to add a little butter before. Cook for 5-6 minutes stirring often. Spoon out excess fat if the salsiccia has released plenty.
When the meatballs are done, add the spinach to the pot and cover. Let the spinach steam a couple of minutes, then stir. It will have softened and lost volume. Return the mushroom to the pot. Stir well and remove from the heat as soon as the mushrooms have gone back up in temperature as the rest of the dish.
Notes
You don't need to blindly follow the quantities in this recipe, as what matters is the process. If you find packages of salsiccia/mushrooms/spinach that are bigger or smaller, just go with what you have. As long as it fits your vessel.
Salsiccia will release some fat that you may want to scoop out. Do not discard it in nature! Pour it in a small bowl aside and let harden, then discard in the trash. Or pour over a used coffee filter with coffee grounds in the trash bag, so the coffee gounds will absorb it and prevent it from leaking.
Please be aware that the nutritional information provided is made with an online calculator and only meant to be used as a guideline.