With a color tantamount to freshness and vibrancy and an aroma redolent of a Provencal breeze, basil oil is like a bit of the Mediterranean in a bottle. The esters and flavanoids in basil -- these are the chemicals responsible for its aroma and taste -- infuse flavor into pure fats like olive oil. For the purest, highest-quality infusion, you need the purest, high-quality ingredients. That means fresh, organic basil and cold-pressed extra-virgin olive oil.
Wash the basil under cold running water and let it air dry overnight in the refrigerator on a tray lined with paper towels.
Choose a bottle that has a rubber stopper instead of a screw cap, then wash it thoroughly. Mix 1/2 cap of bleach with 1/2 gallon of water and pour it into the bottle. Let the bleach water sit in the bottle for 15 minutes, then rinse and let the bottle air dry.
Snip the basil leaves from their stems and stack them. Measure equal parts basil and oil, by volume; stack but do not compress the leaves in a measuring cup to determine the volume. Press the basil leaves gently with the bottom of a spoon to bruise them.
Roll the basil leaves into a tight cylinder and drop them into the jar. Pour extra-virgin olive oil into the bottle and seal it with the stopper. Mince the leaves instead of leaving them whole if you want a medium- to dark-green basil oil.
Set the bottle in a cupboard or pantry for one week. Taste the oil after one week and every day thereafter until it reaches the desired flavor.
Strain the oil through a sieve lined with cheesecloth and into a bowl. Transfer the oil back into the bottle with the rubber stopper.
Store basil oil in the refrigerator for as long as three days. Store basil oil in the freezer for as long as three months.
For a faster infusion, heat the basil leaves and olive oil in a saucepan until they reach 180 degrees Fahrenheit, then steep for 30 minutes. Heat, however, does degrade the olive oil and aroma of the basil.
Add spices and aromatic ingredients, such as peppercorns and garlic cloves, along with the basil to create your own flavor creations.
Use basil oil as a cold finishing ingredient, for the best results. Drizzle it over mozzarella and tomatoes, for example, or incorporate it into a salad dressing. Cooking changes the taste and color of the oil.
Infused oils carry the risk of botulism. Sanitize the bottle, use high quality ingredients and air dry the basil before you infuse the oil to reduce the risk.