Instructions:
- Preheat oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.
- Peel and slice the yams uniformly. Arrange the yam pieces in a single layer in the prepared baking dish. Dot the top evenly with the cubed butter.
- In a separate bowl, vigorously whisk together the white sugar, brown sugar, water/juice, vanilla extract, cinnamon, nutmeg, and salt until the sugars are mostly dissolved.
- Pour the glaze mixture evenly over the yams in the baking dish, ensuring every piece gets some liquid.
- Cover the baking dish tightly with foil and bake for 30 minutes to steam the yams.
- Remove the foil. Return the dish to the oven and bake for another 20–35 minutes, basting once halfway through, until yams are tender and the glaze is thickened.
- Let the dish rest for 5–10 minutes before serving to allow the syrup to set slightly into a sticky glaze.