Steam the pumpkin in the steamer until soft. Drain well and mash. Add brown sugar and cinnamon, cook over low heat, stirring constantly. Cool to room temperature, and add walnuts. Unfold phyllo. Take two sheets and dot with softened butter or brush with melted butter. Spread 1/2 cup of the pumpkin mixture across the width of the sheet. Fold in the two short end to seal in the pumpkin. Roll into a cylinder and then coil into a spiral. Repeat and keep adding to the spiral. Brush with melted butter. Bake in a preheated 425 degree oven until slightly brown. Reduce heat to 350 and bake for 40 minutes.