Sweet and savory kalbi butter is a riff on the traditional flavors of Korean BBQ. A mash-up of soy sauce, sesame oil, garlic, brown sugar and soft butter makes for a super-versatile compound butter. Put it on fish, chicken, or roasted vegetables, especially sweet potatoes. Make a double batch so you can have some now and more later.
Sweet potatoes: Preheat oven to 375 degrees F. Coat potatoes in corn oil, then roll in sea salt. Wrap in aluminum foil and bake until soft, 1 hour.
Kalbi butter: Simmer soy sauce, sugars, and sesame oil in a small saucepan over high heat, just until sugars are dissolved, 1–2 minutes. Turn heat off to cool slightly, 5 minutes; soy mixture should still be warm, but not hot.
Meanwhile, in a food processor, pulse garlic, ginger, and chili flakes until blended. Add the softened butter and pulse to incorporate. With the motor on, drizzle in the warm soy liquid, a little at a time, to fully combine with the butter mixture. Transfer this compound butter to a bowl and set aside. (Note: Can be stored in an airtight container for several weeks.)
Assembly: Remove sweet potatoes from oven. Transfer to a plate and split down the middle. Spoon in a generous amount of kalbi butter. Garnish with scallions, sea salt, and chili flakes. Serve immediately.