how to make polish zapiekanke

We posted about enjoying the "zapiekanke" pizza bread we had in Krakow. It is basically pizza bread, but with sauteed mushroom paste instead of tomato sauce, topped with melted cheese and squirts of ketchup or other sauce (like hot sauce!). To make the mushroom paste, I picked up a pound of white mushrooms from the farmers market, chopped them finely in a food processor and sauteed with margerine, salt, and pepper. I froze a thin sheet of this in a freezer bag so I'll have some for later.