Step 1: Wash and peel the sweet potatoes. Slice them into uniform 1-inch thick rounds or halves, depending on their size.
Step 2: In a large saucepan or Dutch oven, combine the unsalted butter, packed light brown sugar, granulated sugar, ground cinnamon, ground nutmeg, a pinch of salt, and water or orange juice.
Step 3: Bring the mixture to a gentle boil over medium heat, stirring constantly until the sugar dissolves completely and the sauce thickens slightly to form a rich glaze.
Step 4: Carefully add the prepared sweet potato pieces to the saucepan, ensuring they are submerged and coated in the sugary syrup.
Step 5: Reduce the heat to low, cover the pot, and let them simmer for about 30-45 minutes, or until the sweet potatoes are fork-tender but still hold their shape. Stir occasionally and gently to prevent sticking and ensure even cooking.
Step 6: Remove the lid and increase the heat slightly to medium-low. Continue to simmer, uncovered, for another 10-15 minutes, allowing the sauce to reduce and thicken into a beautiful, glossy glaze.
Step 7 (Optional): For extra caramelization, transfer the tender candied yams to a baking dish and bake in a preheated oven at 375°F (190°C) for 15-20 minutes, or until the edges are slightly caramelized and bubbly.
Step 8: Remove from heat and serve warm. Garnish with chopped pecans or toasted marshmallows if desired.