Chef Charles Namba of Los Angeles restaurant Camélia—named one of 2025’s Best New Restaurants—has reimagined the classic sweet potato gratin into a modern French-Japanese side dish rich with miso butter, cheese, and nori. Inspired by a nostalgic childhood trick where his mother microwaved Japanese sweet potatoes with cold butter, Namba developed a streamlined recipe that trades tedious slicing for effortless mashing to create an elevated holiday staple.

Rethinking the Classic Base With Japanese Sweet Potatoes

Traditional gratin recipes typically rely on a mandoline slicer to create thin, uniform layers of standard orange sweet potatoes. Chef Namba departs from this labor-intensive method by using large chunks of cream-colored Japanese sweet potatoes boiled until tender and gently mashed with a salty-sweet miso butter. Naturally sweeter, starchier, and denser than typical varieties, Japanese sweet potatoes impart a velvety texture without requiring extra fuss or complex layering.

For home cooks unable to source Japanese sweet potatoes, standard orange sweet potatoes or garnet yams serve as suitable substitutes. Skipping the mandoline significantly reduces preparation time while preserving the richness expected from a festive casserole.

Building Umami and Texture

To assemble the gratin, the miso-infused potato mixture is spread evenly into a casserole dish. It is then finished with a coating of shredded cheese, freshly chopped chives, and nori. When baked, the dish develops golden-brown, crispy edges that contrast with the creamy interior.

The combination of savory miso, rich cheese, and earthy nori provides a balanced umami depth, transforming a comforting classic into a versatile side dish suitable for any dinner table or holiday feast.

Chef’s Note: Sourcing and Substitutes

Japanese sweet potatoes can typically be found in well-stocked grocery stores and international markets. Identified by their dark purple skin and pale flesh, they offer a sweeter flavor profile and a denser texture than standard varieties. If unavailable, standard sweet potatoes can be used as an accessible alternative without altering the overall cooking process.