Make your own bread crumbs: Cut fresh bread into cubes. Place them on a baking sheet and bake at 350F until crisp, about 15-20 minutes. Process the cubes in a blender or processor until finely ground.
Heat the oil, butter or margarine in a medium skillet and add onions. Lower the heat, and cook, stirring frequently, until browned. Let cool slightly.
Meanwhile, bake or steam the potatoes until just tender. Peel and mash them or put them through a ricer. (Do not whip the potatoes - some texture is necessary).
Combine the potatoes and onions, and stir in egg or egg substitute and seasonings.
Preheat the oven to 375°F Spray a baking sheet with nonstick cooking spray and set aside.
Unroll the phyllo and carefully peel apart 12 sheets. (Return the remaining phyllo to your freezer for another use) Cover 6 sheets with a damp dishcloth to prevent drying.
Brush 1 sheet lightly with the melted butter or margarine. Quickly lay the second sheet on top, and brush with butter or margarine. Continue this process with remaining 4 sheets.
Sprinkle half of the bread crumbs over the phyllo, then spoon half the potato/onion mixture in a ribbon across the width (short side) about 4 inches in from the edge.
Fold this 4-inch edge over to cover the filling, then roll into a cylinder. Carefully transfer the filled roll to the prepared baking sheet.
Repeat procedure with the remaining 6 sheets of phyllo, bread crumbs and potato-onion mixture.
With a very sharp knife, cut partially through the rolls at 2-inch intervals, leaving the rolls intact and being careful not to separate the slices. Brush the tops very lightly with melted butter or margarine and bake until golden brown, about 30-40 minutes.