This has everything you want in a stir-fry: delicious bok choy, with its wonderfully creamy stems; sharp daikon radish; crusty pan-fried tofu; and a load of spice. Tempeh, the nutty fermented soybean cake, also goes beautifully with bok choy. If you want to use it in place of the tofu, crumble it into the hot oil and stir until it’s crisp, 5 to 7 minutes.
1 head bok choy 4 tablespoons vegetable oil 1 block firm tofu (about 1 pound), cut into 1/4-inch slices and patted dry 1 onion, chopped 1 tablespoon minced garlic 1 tablespoon minced ginger 1 or 2 hot chiles (like jalapeño or Thai), seeded and minced 8 ounces daikon radish, cut into 1⁄4-inch coins 2 tablespoons soy sauce, or to taste black pepper
Cut the leaves from the stems of the bok choy. Trim the stems as necessary, then cut them into 1-inch pieces. Cut the leaves into wide ribbons and keep them separate from the stems.
Put 2 tablespoons of the oil in a large skillet over medium heat. When it’s hot, slide in the tofu, working in batches if necessary to avoid overcrowding the pan. Cook until the bottoms are crisp and golden, 3 to 5 minutes; carefully flip and cook for another 3 to 5 minutes on the other side. When the tofu slices are done, transfer them to paper towels to drain.
Add the remaining 2 tablespoons oil to the pan and raise the heat to medium-high. When it’s hot, add the onion, garlic, ginger, and chile and cook, stirring, for just 1 minute. Add the bok choy stems and daikon and cook, stirring occasionally, until they just lose their crunch, about 3 minutes.
Add the bok choy leaves and about 1⁄2 cup water. Cook, stirring occasionally, until the liquid evaporates and the stems and radish are fully tender, 5 to 10 minutes; add a little more water if necessary. Return the tofu to the pan, stir in the soy sauce, and sprinkle with black pepper. Taste and adjust the seasoning. Serve hot or at room temperature.