Blend flour, salt, and pepper into hot butter in a saucepan.
Heat until bubbly.
Remove from heat.
Add milk gradually, blending thoroughly.
Bring to boiling; stir and cook 1 to 2 minutes.
Blend mayonnaise into sauce.
Add mixture slowly to beaten eggs, stirring well.
Lightly mix in grated onion and cooked broccoli.
Pour mixture into a greased 1 1/2 quart ring mold.
Set mold in a pan in a 300Â°F oven.
Add boiling water to pan to a depth of 1 inch.
Bake about 35 minutes, or until custard tests done.
Unmold onto warm serving plate.
Serve with creamed chicken garnished with strips of pimiento and mushrooms lightly browned in butter.