Mash until smooth. Spray ring mold with Pam. In bottom of ring mold, spread thickly 3 tablespoons butter. Add 1/2 cup chopped pecans. Then add 1/2 cup dark brown sugar on top. Pack in potato mixture. Bake in pan of hot water at 350 degrees for 35 or 40 minutes or until done. NOTE: Can be prepared ahead of time and left in refrigerator until time to bake.