Flavored oils must be refrigerated, and most will hold their quality for at least 1 week. Prepare only as much as you will use in that time. For optimum flavor and texture, bring the amount of oil you will be serving to room temperature.

This cold infusion is the easiest to make. Use in vinaigrettes, drizzle over poached shellfish or grilled fish, chicken, or vegetables just before serving, or stir into hot tomato soup.

Combine in a sterilized 8- to 10-ounce jar:

Cover and shake the jar gently, then let steep in the refrigerator for up to 4 days. Strain the oil through a dampened paper coffee filter. The oil can be kept, covered and refrigerated, for no longer than 1 week.

Blanching the herbs sets their color and tints the oil an alluring green. If using rosemary, reduce the amount by half. To skip the filtering and give the resulting condiment more body, see Jen’s Basil Oil.

Have ready a bowl of ice water. Bring a pot of water to a boil. Blanch for 10 seconds in the boiling water:

Remove them quickly with a strainer and dunk in the ice water, swishing them around to be sure they’re all cold. Remove from the water and squeeze gently to remove the excess water. Coarsely chop the herbs and transfer to a blender. Add:

Blend until the herbs are pureed. The mixture will be very frothy. Let the puree settle for about 30 minutes. Pour into a jar through a fine-mesh sieve lined with several layers of cheesecloth or a coffee filter and leave to drain overnight. The next day, very gently push down on the solids to extract as much oil as possible. Use immediately or cover and refrigerate for up to 1 week. For the best flavor, let the oil come to room temperature before using.

Capsaicin, the compound responsible for the spiciness of chiles, is very effectively transferred to the oil, which, in turn, coats the tongue. Until you determine just how spicy the oil is, use sparingly and to taste. A few drops are superb in dipping sauces for dumplings or in dressings for vegetable dishes. If desired, add a few wide strips of orange zest, a cinnamon stick, or a tablespoon of Sichuan peppercorns for a more complex flavor. For a similar condiment, see Spicy Chinese Chile Crisp.

Have ready:

Or, coarsely grind in a blender or spice grinder:

Transfer to a small saucepan and add:

Heat over medium heat until the oil reaches 350°F, or until large bubbles appear. Remove from the heat, cover, and let sit for at least 4 hours.

Once cool, you may leave the oil unstrained, transfer to a sterile jar, and serve with a spoon for adding the chile flakes to dishes at the table. For a clear oil, pour through a fine-mesh sieve that has been lined with several layers of cheesecloth or a coffee filter. Push down on the solids to extract as much oil as possible. Cover and refrigerate for up to 1 month.