The phrase “basil dressing” describes any sort of sauce or marinade that features the herb basil as a primary ingredient. There are many sorts of basil dressings. Some are designed for use on salads, while others are intended as a flavorful marinade or as an accompaniment for grilled meats. Basil dressing can be creamy or runny, savory or sweet. Virtually any dressing that includes basil can properly be called a basil dressing.
Basil dressings are often available commercially, usually near other salad dressings or in the herb display of grocery stores. Many prepared marinades also include basil or basil flavorings. It is also usually fairly easy to make basil dressing at home. Cooking with basil is usually quite easy, so long as the basil is fresh.
Fresh basil is the only really essential ingredient in basil dressing. Basil is an herb that grows well in most climates and is widely available throughout much of the world. In dressings, the leaves are picked fresh, then either chopped or shredded directly into the dressing base. Once picked, basil will typically stay fresh for up to a week; longer if it is preserved in the oils and vinegars so common to dressings. Basil used in dressings is never cooked.
Dried basil is a popular spice staple, but its flavor is usually quite different from fresh leaves. Replacing dried basil for fresh is not usually recommended in basil dressing. A lot of basil’s signature flavor is usually lost in the drying process. Dried basil can lead a dressing's taste to fall flat, or at least lack the bite it was designed to impart.
Most of the basil available in the U.S. and Western Europe is known as sweet basil. This sort of basil is wide-leaved and has a mild flavor. It is widely used in Italian foods and in dressings designed to accompany green salads and grilled meats. Any sort of herb salad or basil salad is usually a good match for a sweet basil dressing.
Thai basil, also sometimes known as holy basil, is a basil variety indigenous to southeast Asia. Many regional dishes from this area, from curries to stir fries, call for Thai basil. This sort of basil grows leaves that are typically smaller and lighter in color than sweet basil. Thai basil usually also has a stronger, sharper flavor. It is often used in dressings to flavor Asian salads, spring rolls, or curried meats.
Different varieties of basil can usually be interchanged with each other without problem. Sweet basil can be used to make an Asian-style dressing, for instance, particularly when combined with soy, peanuts, citrus, or other regionally-appropriate flavors. Similarly, Thai basil can be used in a simple grilled chicken marinade in place of sweet basil, but may need to be tempered with a bit of balsamic vinegar or blended with olive oil for a more authentic flavor.
There are no defined limits on how basil dressing should or should not be made. Some varieties are creamy, often incorporating yogurt or mayonnaise. Others are oil and vinegar-based. Most basil dressing varieties include lemon juice and sometimes also garlic or shallot. Making basil dressing at home gives cooks some leeway in determining the overall quantity of dressing, as well as the strength of basil or other flavors, and often also allows for a bit of tailoring to make the dressing match the flavors of whatever it is meant to accompany.