On the lookout for Japanese knotweed recently, I passed a lush patch of young garlic mustard - Alliaria petiolata, a weed so devious it secretes chemicals to inhibit the growth of other plants in its vicinity. It is described as a noxious weed.
Naturally, I felt I should eat it.
I could tell by its sappy flower stalks that it was second year field garlic - the plant is biennial, meaning it lives two years. The flowers only form in the second year. It was growing in the shade, and I know from experience that shade renders bitter plants sweeter (dandelions, too), so I picked a great big bunch, snapping the stems where they were still tender. A woody or fibrous stems means the pant is too mature to make a good pesto - too bitter and too stringy.
The world does not need another pesto recipe. I know that. And I know that one can use just about any leaf, any cheese, and any nut. But I remain attached to the first, classic pestos I made, instructed from the page by Marcella Hazan. Pine nuts, parmesan, olive oil and butter. I buy Spanish pine nuts, so this is not exactly an economical recipe, but a little does stretch quite a long way. I am allergic, as far I can tell, to the Chinese kind. They give me a bitter mouth for ten days. Currently, Spanish pine nuts ring in at $40 a pound. Holy moly.
You can use garlic mustard's leaves, flowers and stems, but only if the stems are still very tender (bite them, to see!). Otherwise, strip the leaves and flowers from the stems. After spring, the leaves become very bitter, and tough.
For about 4 cups of pesto:
1 large bunch garlic mustard, roughly chopped (yield is about 8 tightly-packed cups)
1 1/2 cups grated Parmigiano Reggiano (the real thing)
1/2 cup pine nuts
4 tablespoons butter
1/2 cup extra virgin olive oil
After washing and drying the garlic mustard put it in two batches into a food processor (a recent gift from the Frenchman; go figure, I wrote a recipe book without a food processor in the house...). Add some of the cheese, butter and oil and pulse gently until each batch is chopped fine and resembles a thick paste. Turn into a bowl and mix the two batches together and taste. Add a little salt (the cheese is already quite salty) and plenty of freshly ground black pepper.
Pack into jars and freeze, and eat some at once, spread on toasted bread, as bruschetta. It keeps well in the fridge for a week. It is also good stirred into soup at the last minute, or whisked into a salad dressing.