Blend all ingredients and whirl until smooth. Let batter stand for an hour.
Heat small size skillet and brush bottom with melted butter. When butter is hot, remove from heat. Pour about ¼ cup of batter. Tilt and rotate pan quickly to cover the bottom with a thin layer. Pour any excess of batter back to the bowl. Return pan to heat. Loosen edges of crêpe with a metal spatula. Cook. Turn crêpe, cook and transfer to plate. Repeat procedure with rest of batter, brushing pan lightly with butter when necessary.
Melt 3 tablespoons butter in a saucepan over medium heat. Add flour and stir until mixture is well blended. Remove from heat and gradually add hot milk, stirring constantly until mixture comes to a boil and thickens. Season with salt, pepper and nutmeg. Separate 1 cup of the béchamel sauce in another bowl. Set aside.
Melt remaining butter with the oil in a deep skillet and add onions. Cook until onions are soft and begin to brown. Add onion to béchamel sauce in the saucepan, together with chopped egg and parsley. Season with salt, pepper and nut meg. Place crepes on a horizontal surface and place 2 or 3 tablespoons of filling along one edge. Roll to enclose filling, leaving ends open.
Arrange crepes, seam side down on a previously greased ovenproof serving dish. Cover with the reserved cup of béchamel sauce.
Sprinkle grated parmesan cheese on top. Broil before serving.