When I visited Tokyo and Kyoto with my friend Devra a couple years back, I didn’t want to leave. I would say it was the beautiful aesthetic, the attention to design and style, the amazingly efficient trains, but really, of course, it was the food. I was especially excited when I learned how much the Japanese revere the sweet potato, one of my all-time favorite foods. In season (fall and winter), street vendors hawk stone-roasted ones—paler-fleshed and sweeter than ours. Famous cookbook author Harumi Kurihara showed me how she loves to mash miso into roasted sweet potatoes, so when I returned home, I knew that even the orange-fleshed varieties here would take beautifully to Japanese flavors. For a kick of bitterness that nicely offsets the earthy miso, use broccoli rabe instead of the broccolini.
You can roast more than one sweet potato at a time and keep it, wrapped in aluminum foil or plastic, in the refrigerator for up to 1 week before reheating it in a low oven or in the microwave while you make the topping. If you can’t find a sweet potato this small, feel free to roast one twice the size (it will take longer, obviously), and just cut it in half.
