Almond-Topped Yam Gratin

Yam that has been boiled, then baked is very different from plain boiled—it has pouf and crunch. The texture, made creamy by mozzarella and lightened with soy milk (to heighten the tuber’s nuttiness rather than impart a more dairy taste) is like souffléd baked potatoes. Tomato paste adds a peach tone and sweet edge but is not strictly necessary. Serve with bitter greens, with (or without) pork roast.