This is an excellent way to preserve summer herbs, garden or Farmers' market fresh, to be used when the winter doldrums hit.
The image above is of green shiso oil, but I have also made sage, dill, parsley, lemon verbena, mint, basil, lovage and purple shiso oils following the same general principle set out below.
3 cups loosely packed herb of your choice (both leaves and stems)
1 1/2 cups vegetable oil
1/4 tsp salt
Bring a pan of water to the boil. Stir in the herb leaves and stems and blanch for 20-30 seconds until the leaves brighten slightly.
Drain immediately and add the herbs to a bowl containing an ice bath of water and a generous amount of ice cubes. Refresh for a minute or so before draining again. You can skip this step, but the oil will not be a pretty green.
Squeeze out the excess water before adding the herbs to a Vitamix or blender, along with the salt and oil. Blitz until the mixture is a bright green and the herbs and stems are finely suspended in the oil.
Pour into a filter lined coffee dripper placed over the container in which you plan to keep the oil. Allow the oil to drip through overnight without forcing the liquid through.
Close your container and refrigerate for use in salad dressings, to dress dishes with a bit of herbal flavor, etc. The herbal sludge that remains in the filter after the oil has dripped though can also be used in dressings, stirred into mayonnaise to elevate salads or eggs to elevate the final product, and can also be frozen in ice cube trays to be used in sauces and dressings over the winter.