What the recipe doesn't tell you
Sauce Making
Using flour, cornstarch, or other starches to give body to sauces, soups, and gravies. A roux (equal parts fat and flour cooked together) is the French approach. A slurry (starch in cold liquid stirred into hot) is the Asian and quick-sauce approach. Both work through starch granules absorbing water and swelling.
Adding flour directly to hot liquid. Not cooking roux long enough — raw flour taste. Adding hot liquid too fast. Over-cooking cornstarch sauce — it thins back out. Using flour and cornstarch interchangeably without adjusting quantity.
Starch granules swell and burst when heated (gelatinisation). Roux cooks flour in fat first to prevent clumping. White roux (2–3 min) thickens most. Blond roux (5–7 min) has nutty flavour. Dark roux (20–45 min, Cajun) has deep flavour but barely thickens. Cornstarch is twice the power of flour and produces clearer result. Slurry must be mixed with cold liquid first.
The complete professional entry for Roux and starch thickening: quality hierarchy, sensory tests, cross-cuisine parallels, species precision.
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