But the two tastes can be one taste ... one beyond one taste.
What is regarded as the preparation of superb delicacies is not necessarily superior, nor is the preparation of a soup of the crudest greens necessarily inferior. When you select and serve up crude greens, if you do so with a true mind, a sincere mind, and a pure mind, then they will be comparable to superb delicacies. Why is that so? Because when one enters into the pure and vast oceanic assembly of the buddha dharma, superb delicacies are never seen and the flavor of crude greens does not exist: there is only the one taste of the great sea, and that is all (Uchiyama: The many rivers which flow into the ocean become the one taste of the ocean; when they flow into the pure ocean of the dharma there are no such distinctions as delicacies or plain food, there is just one taste, and it is the buddhadharma, the world as it is). Moreover, when it comes to the matters of nurturing the sprouts of the way and nourishing the sacred embryo, superb delicacies and crude greens are as one; there is no duality. There is an old saying that a monk's mouth is like a stove (meaning that a stove consumes all kinds of wood equally, regardless of its quality). You must not fail to understand this. You should think that even crude greens can nourish the sacred embryo and nurture the sprouts of the way (Uchiyama: Likewise, understand that a simple green has the power to become the practice of the Buddha, quite adequately nurturing the desire to live out the way). Do not regard them as base; do not take them lightly. A teacher of humans and devas is able to regard crude greens as things that convert and benefit [beings].
From: Tenzo Kyokun - Instructions for the Cook by Eihei Dogen - Translated by Griffith Foulk