A roux is a fundamental culinary component formed by cooking equal parts fat (usually butter) and flour together. The cooking process, which dictates the roux's color and resulting flavor, transforms the raw flour's taste and creates a thickening agent. A white roux (cooked briefly) is delicate, while a brown roux (cooked longer) imparts a nutty, richer flavor. The roux serves as the base for many sauces, including the classic béchamel, providing the necessary thickness and texture. The longer a roux cooks, the darker and more intense its flavor becomes.