Herbs vs. Spices

• Herbs and spices contain very similar flavor compounds -- often the same ones, in fact -- but they come from different parts of the plant. The blossoms and leaves of a plant are generally considered herbs, while the seeds, bark and roots provide spices. Sometimes, as with anise seed and fronds, one plant produces both herb and spice with a similar flavor. Coriander is the opposite, with its seeds and fresh leaves -- better known as cilantro -- providing very different flavors. There are several ways to infuse your sauces with the flavor of fresh or dried herbs, each with its own strengths and weaknesses.

The Direct Approach

• The simplest way to add herbal flavors to your sauce is by adding them directly, and allowing them to simmer. This requires little or no preparation, other than chopping the herbs. Leaving the herbs in full stems is a useful technique when you don't want green flecks in the sauce, or when you're using an herb such as rosemary or dill that is very potent. You can simply remove the stem once it has infused enough. As a rule dried herbs can be added earlier, so their flavor has longer to infuse, while fresh herbs should be added at the end to retain their bright flavors. Finely chopped herbs infuse more quickly than herbs in large pieces, but also fade more quickly.

Infusing Your Liquid

• If your sauce is based on a liquid such as broth, cream or wine, you can infuse the herbs into that liquid ahead of time for a subtler finish. Simply preheat the liquid to a simmer, then drop in your herbs. Taste it regularly until you're happy with the strength of the flavor, then remove the herbs. Some cooks use a French press coffee maker instead, using the plunger to seal off the herbs and stop the infusion. For a more intense flavor, use a large quantity of herbs and simmer them until their flavors -- and the liquid -- are highly concentrated. Keep it refrigerated, and add a splash of this decoction to your sauces as needed.

Infuse into Fat

• A quirk of the volatile flavor molecules found in herbs is that they often infuse better into fats than into water-based liquids. Even more importantly, the molecules are less volatile once they're trapped in the fat, which means the flavor lasts longer and holds up better in cooking. Gently simmer chopped or whole herbs in butter or oil for 30 to 50 minutes, to extract the flavors. Once strained and chilled, you can use the butter to make a sauce-thickening roux, or whisk it in at the last minute to enrich, flavor and give body to your sauce. Oils can be drizzled over the finished dish, or incorporated into emulsified sauces, such as mayonnaise and salad dressings.