Truly Candied Yams

Ingredients

• 2 1/2 pounds sweet potatoes, peeled and sliced crosswise into 1/2-inch-thick rounds
• 1 cup light brown sugar
• 1/4 cup unsalted butter
• 1/2 cup water
• 1 tablespoon Diamond Crystal kosher salt; for table salt, use about half as much by volume or the same weight
• 1 tablespoon apple cider vinegar
• 1/8 teaspoon ground cinnamon
• 1/8 teaspoon ground allspice
• 1/8 teaspoon ground ginger

Directions

1. Arrange the sweet potato slices in a 9- by 13-inch baking dish in a single, level layer, letting them overlap as needed so they all fit. Put the dish aside for the moment.
2. In a small saucepan, add the brown sugar, butter, water, and salt. Bring the mixture to a boil, stirring frequently, and cook until an instant-read thermometer reads 220 degrees F (104 degrees C). Mix in the cider vinegar, cinnamon, allspice, and ginger. Pour the syrup over the sweet potatoes, using a spoon to coat any dry spots so every slice is moistened.
3. Cover the baking dish tightly with aluminum foil and set it in a cold oven. Set the oven to 250 degrees F (120 degrees C) and let it heat with the dish inside. Bake until the potatoes are tender all the way through, about 1 hour 15 minutes, turning them over and spooning syrup over them every 20 minutes. The exact time can vary with your oven, dish, and potato size, so take a peek as they cook.
4. Take off the foil and keep baking, turning and basting the potatoes now and then, until they are extremely soft and coated in a deep brown syrup, about 30 minutes more. Cool them briefly before serving.