Milk Sauce

Dissolving the flour in cold milk first prevents lumps by allowing starch granules to separate before heating. When heated, these starch granules gelatinize and thicken the sauce through a process called gelatinization. Creaming the butter and sugar creates an emulsion that helps stabilize the sauce, while the egg provides additional emulsifying lecithin and creates a smooth, custard-like consistency. Heating to just below boiling (around 180-185°F) cooks the egg and activates the starch without curdling the proteins.