What are two key ingredients in making french sauces?

1. Roux: A roux is a mixture of equal parts flour and fat (usually butter) that is cooked together until it reaches a desired color. It is used as a thickening agent for sauces and soups.

2. Stock: Stock is a liquid that is made by simmering bones, vegetables, and herbs in water. It is used as a base for many French sauces.