1. Cut off the lower, tough parts of the stalks, stripping off all but the uppermost leaves. Wash well and put in a saucepan with boiling water to half-cover the stalks. Cover and cook until tender about 15 minutes. Drain well. Arrange stalks in a buttered shallow baking dish.
2. Melt the butter in a small saucepan and saute the onion until tender. Stir in the flour and cook for 1 minute.
3. Gradually blend in the milk; bring to a boil, stirring. Add salt to taste and the mace and cook over hot water for 15 minutes, stirring often.
4. Preheat the oven to 400 degrees.
5. Remove sauce from the heat and stir in the cheese. Pour over the pokeweed. Cover loosely with aluminum foil and bake for 15 minutes. Sprinkle with bread crumbs before serving.