Step 1: Preheat your oven to 375°F (190°C). Peel the sweet potatoes and slice them into even 1/2-inch thick rounds or chunks. Arrange them in a large baking dish.
Step 2: In a medium saucepan, melt the unsalted butter over medium heat. Add the dark brown sugar, granulated sugar, ground cinnamon, ground nutmeg, allspice, and salt. Stir constantly until the sugars are fully dissolved and the mixture is smooth and bubbly.
Step 3: Carefully pour in the water (or orange juice) and vanilla extract. Bring the mixture to a gentle simmer, stirring occasionally, and let it cook for 2-3 minutes until it slightly thickens into a syrupy glaze. Remove from heat.
Step 4: Pour the prepared brown sugar glaze evenly over the sweet potatoes in the baking dish, ensuring every piece is coated.
Step 5: Cover the baking dish tightly with aluminum foil. Bake for 30 minutes. This allows the sweet potatoes to tenderize in the flavorful glaze.
Step 6: Remove the foil. Gently stir the sweet potatoes to re-coat them with the glaze. Return the dish to the oven, uncovered, and continue baking for another 15-25 minutes, or until the sweet potatoes are fork-tender and the glaze has thickened and caramelized. Stir once or twice during this period for even cooking and caramelization.
Step 7: Remove the candied yams from the oven and let them rest for a few minutes before serving. The glaze will thicken as it cools. Serve warm and enjoy your perfect candied yams recipe!