Preheat oven to 350 degrees. Soak the porcinis in water and set aside. Heat the oil in a large saute pan, medium hot. Pat dry the fish. Mix the Cedarburg/Ukrainian seasoning with the flour and dredge the filets in the flour mix. Shake off any excess flour, and saute both sides until brown. Remove and finish in the oven.
Julienne the mushrooms, slice the leeks and stem the spinach. Save the water from the mushrooms. In the same pan, on high heat, saute the mushrooms and leeks. Add the lemon juice, mushroom water, shallots and porcini powder. Reduce by half, add the spinach and reduce until almost no liquid, stirring frequently. Add the cream and reduce again until desired thickness. Add salt and pepper to taste. Remove fish (should be done by now) from the oven. Serve the sauce over the fish with a side of jasmine or basmati rice.