Preheat oven to 350 degrees F. Lightly grease shallow 2 1/2-quart ceramic baking dish. In medium bowl, with fork or wire whisk, mix buttermilk, pumpkin, egg yolks, and 2 tablespoons chopped chives.
In 4-quart saucepan, heat margarine or butter and 1 1/2 cups water to boiling over high heat. Remove saucepan from heat. In small bowl, with wire whisk, mix cornmeal, brown sugar, baking soda, salt, and pepper. Gradually whisk cornmeal mixture into hot liquid in saucepan until blended. Then whisk in pumpkin mixture.
In small bowl, with mixer at high speed, beat egg whites just until stiff peaks form. Gently fold egg whites, one-third at a time, into cornmeal mixture until blended. Spoon batter into baking dish and sprinkle with remaining 1 tablespoon chives.
Place baking dish in roasting pan on oven rack. Pour boiling water into roasting pan until it reaches halfway up side of baking dish. Bake spoon bread 50 to 55 minutes until lightly browned and puffed and knife inserted 2 inches from center comes out clean.
Cook Time: 55 minutes
Total Time: 1 hour 30 minutes