In a small bowl, combine flour and salt; cut in the shortening until crumbly. Gradually add water, tossing with a fork until a ball forms. Roll out pastry to fit two 4-1/2-in. tart pans with removable bottoms. Transfer pastry to pans. Trim pastry to 1/2 in. above top of pans; flute edges above edge of pans. Prick bottom and sides of pastry with a fork. Line shell with a double thickness of heavy-duty foil. Bake at 450° for 8 minutes. Remove foil; bake 4-6 minutes longer or until light golden brown. Reduce heat to 375°.
Meanwhile, in a skillet, saute mushrooms in butter until tender. Remove from the heat; add the ham and cheese. Spoon into tart shells. Combine egg and cream. Pour over mushroom mixture. Bake at 375° for 20-25 minutes or until a knife inserted in the center comes out clean. Let stand for 5 minutes before serving.