In a large ziplock bag, combine cornstarch, salt, pepper, sugar, chicken broth, ½ the soy sauce, and wine. Add chicken and toss to coat. Seal the bag and refrigerate for at least 2 hours or up-to 6.
Bring potato cubes and water to cover to a boil. Cook until softened but still firm in the center, about 7-9 minutes. Drain and put in a bowl.
Preheat oven to 375°F (190°C). Whisk the coconut milk, evaporated milk, and ½ cup of water in a bowl.
In a wok or deep skillet, heat oil over medium-high. Add onion and curry powder, stirring until soft, about 7-8 minutes. Add the chicken and brown on both sides, another 5-6 minutes. Add the potatoes and remaining soy sauce and continue cooking another minute. Stir in the coconut milk mixture and bring to a simmer. Cook about 20 minutes more until the potatoes and chicken are cooked through and the sauce has thickened.
Pour everything into a baking dish large enough to hold the chicken in a single layer, skin side up. Bake until the top is browned, about 15-20 minutes. Remove and serve over jasmine rice.