Bake, covered, in preheated oven, about 40 minutes. Uncover and gently stir potato mixture. Bake, uncovered, until potatoes are tender, 25 to 30 more minutes. Transfer potatoes to a serving bowl with a slotted spoon; pour syrup over potatoes. Serve immediately.
Make it ahead: Assemble up to 3 days in advance. Make the recipe through Step 3, store it covered in the refrigerator, and then bake it on Thanksgiving Day.
Candied Yams with Rosemary and Orange: Omit vanilla extract, ground cinnamon, and ground nutmeg. Prepare recipe as directed, stirring 1 Tbsp. orange zest and 1 1/2 tsp. chopped fresh rosemary in with salt after removing from heat in Step 2. Proceed as directed, and garnish with small fresh rosemary sprigs and orange zest.