Step 5: Continue to whisk as it cooks another few minutes and thickens.

A roux is a classic thickener in French Cuisine– it’s a simple combination of melted butter and flour, and then a liquid (with stock, it’s known as a “velouté,” or with milk it’s a “béchamel.”) Find out more about the science behind starches here. This amazing technique will help thicken up your soups, add oomph to your chowders, or be the vehicle for an easy white sauce for pasta.

The basic ratio: 2:2:1 — two tablespoons butter, two tablespoons flour, & 1 cup liquid.