Herb Oil, Revisited

The results of two different herb oil techniques.

Many years ago I posted about my default herb oil procedure, which I learned from The French Laundry Cookbook. In a nutshell:

  • blanche herbs,
  • shock in ice water,
  • ring out as much moisture as possible,
  • purée in a powerful blender with oil,
  • let stand overnight (optional, but recommended),
  • strain through a coffee filter.

Most of the herb oil recipes in The French Laundry Cookbook call for 4 cups of fresh herbs and 3/4 cup oil to yield only 1/3 cup herb oil.

I have sworn by this procedure for years. However recently I was reading the “Oils and Dressings” section at the back of the Eleven Madison Park cookbook, and while the Tarragon Oil follows the same procedure, several others follow a rather different one. I would summarize the EMP procedure as such:

  • Combine herbs and oil in a blender and purée thoroughly on high speed.
  • Transfer mixture to saucepan and cook over medium heat, whisking vigorously, until the oil reaches 220°F.
  • Chill the oil over ice.
  • Strain through a coffee filter.

What is really interesting is that these EMP recipes also start with 4 cups of fresh herbs, but then use 1 1/2 cups oil, and yield a whopping 1 cup of herb oil. If the depth of colour and flavour is comparable to the French Laundry oils, this is a significant improvement in yield.

I made two batches of parsley oil, one using the French Laundry recipe, and one using the EMP recipe, and examined them side by side. Here are the results:

  • Colour. The shades of green are very similar, with the EMP version being only slightly darker.
  • Flavour. The French Laundry version has a nice parsley flavour. The EMP version is almost devoid of flavour.
  • Yield. In my test the French Laundry version yielded even less than the recipe predicted. So from the same amount of herbs the EMP version yielded almost 4 times the amount of herb oil.

So the flavour of the EMP version needs to be addressed. On reflection, it is odd that the EMP recipe specifies to cook the mixture to 220°F. To achieve this temperature that so far exceeds the boiling point of water, you have to boil the herb mixture for a few minutes and drive off excess moisture. However in blanching the herbs would never go about 212°F. I think it is this excessive cooking that destroys the herb flavour in the EMP recipe. In other words, instead of cooking the mix to 220°F, it should be sufficient to simply bring the mix to a simmer, and then immediately chill over ice.

I will give this adjusted method a try. If it is able to preserve the flavour of the herbs, this is a real game-changer.