Many people prefer to make oils using fresh herbs, and you certainly can. But I find that high-quality dried herbs, which don’t have the water content of fresh herbs, in most cases make a better oil. Water and oil don’t mix well; water in herbal oil can introduce moisture and bacteria, which leads to spoilage. When I make oils from fresh herbs, before adding the herbs to the oil, I usually freshwilt them: I place them on a basket or screen in a single layer, in a warm area out of direct sunlight, and let them wilt for several hours. They’re ready when they look limp. Fresh wilting allows some of the moisture to evaporate, so there’s less chance of spoilage.