Originally from bon appetit.
2 lb medium sweet potatoes (about 3), scrubbed, halved lengthwise
3 scallions, white and pale green parts only
1/2 cup (1 stick) unsalted butter
1 tbsp unsweetened cocoa powder, preferably Dutch-process
2 tsp pure maple syrup
1 tbsp soy sauce
2 tbsp extra-virgin olive oil
1 tbsp plus 1 tsp toasted sesame oil
2 tbsp toasted white sesame seeds
2 tsp Diamond Crystal or 1 1/4 tsp Morton kosher salt
Roast sweet potatoes in oven at 400* with salt cut side down for 40-50 mins.
Heat butter for 4 minutes, transfer to bowl and whisk in sesame seeds, sesame oil, soy sauce, cocoa powder, maple syrup.
Cut scallions crosswise transfer to bowl of ic water and soak for 10 minutes.
Transfer sweet potatoes to a platter and top with butter and scallions.