Cut a large piece of baking paper and brush the inside with the oil. Distribute the washed spinach leaves (thawed if frozen) evenly in the middle and place the asparagus stalks on top of the spinach. Cut the cleaned mushrooms into quarters or sixths, depending on their size, and spread over the asparagus with the washed and halved cherry tomatoes and spring onions. Season the packet with salt and pepper.
Season the fish with salt and pepper and place on the bed of vegetables with the sprig of rosemary. Drizzle the whole thing with a little lemon juice. If you like, you can add some fresh garlic.
Fold the parcel like a present (maybe fix it on the sides with a stapler if it doesn`t hold up like that).
Cook the vegetable parcel in a preheated oven at 180 ° C. Depending on the size of the salmon, 20-30 minutes. If you want the fish to be translucent, you should leave the parcel in the oven for a maximum of 18 minutes. It is usually cooked through at 20 minutes.