Season the schnitzel with sea salt and paprika. Lightly oil a baking dish and place the schnitzel side by side. Spread the forest mushrooms on top while they are still frozen.
Fill the cream in a measuring cup and add the sauce powder. Mix vigorously with the whisk and pour evenly over the mushrooms and schnitzel.
Place the casserole dish on the middle rail in the oven preheated to 200 degrees for about 30 minutes.