Preheat oven to 450 degrees. Clean the mushrooms. Remove the stems and reserve. Parboil the mushrooms in just enough water to cover, for 3 minutes, until barely cooked. Drain well, blot with paper towels, and set aside until needed. If the tip of the stems seem woody, trim them away. Chop stems coarsely. Melt 2 tb of the butter in a skillet. Toss the chopped mushrooms stems and scallions. Saute until tender and most of the mushroom juices have evaporated. Toss in the pecans, bread crumbs, parmesan cheese, and remaining tablespoon of butter. Stir unitl the butter is melted and absorbed. Stir in the garlic bechamel. Add salt and freshly gournd pepper to taste. Stuff each mushroom cap with the mixture, moiunding it neatly over the top. Sprinkle each with some cayenne pepper. Put stuffed mushrooms in a lightly oiled, shallow baking dish. Bake for 10 minutes or until heated through. Serve at once. Garlic Bechamel: Scald milk. Make puree from roasted garlic. Melt the butter in a heavy saucepan and whisk in the flour. Let this roux cook over low heat, stirring constantly for 3 to 4 minutes. Whisk in the scalded milk. Bring to a boil. Reduce the heat and cook gently, stirring frequently, for 10 to 15 minutes. Add salt and pepper and whisk in the garlic puree. Remove from the heat. Beat the egg in a bowl. Beat som of the sauce into the egg. Next beat the egg mixture back into the garlic sauce. Taste and correct seasonings. Store in the regrigerator, with plastic wrap placed directly on the surface of the sauce, until needed. Thin with milk before using if necessary. .