Slice sweet potatoes into round slices, about 1/4 inch thick.
Melt butter over medium heat in a large skillet and add sweet potato slices to the skillet.
Pour sugar and water over sweet potatoes. Stir gently, reduce heat to low, and then cover with a lid and cook until the sweet potatoes are fork tender, about 1 hour.
Remove from heat and stir in vanilla extract. Spoon the glaze over the sweet potatoes. The glaze with thicken as it cools.
Notes
Baked Candied Sweet Potatoes:While my Grandmother's original recipe was made in a skillet on the stovetop, you can also bake this delicious side dish in the oven. Here's how.Preheat the oven to 425º F. As the oven preheats, melt the butter in a 9x13 baking dish in the oven. Once the butter has melted, carefully swirl the baking dish to make sure the bottom and sides are well coated. Then, add the sugar, water, vanilla extract, and the optional seasonings (if using). Add the sweet potato slices and toss to coat. Bake until fork tender, about 1 hour, spooning the glaze over the sweet potatoes halfway through baking. Cover the baking dish with foil the last 30 minutes of baking.Storage Tips:To store. Cool and store covered in the refrigerator for up to 3 days. Reheat in the microwave or in a 350º F oven until warm throughout, about 30 minutes. Spoon the glaze over the sweet potatoes and serve.To make ahead. Use the baked candied sweet potatoes recipe variation. Prepare the candied sweet potatoes through coating the sliced sweet potatoes. Wrap the baking dish tightly and store in the refrigerator overnight. Remove from the refrigerator while the oven preheats. Bake as directed checking to make sure fork tender.To freeze. Cook and cool the candied sweet potatoes. Store in an airtight, freezer-safe container for up to 3 months. Thaw in the refrigerator overnight. Reheat in the microwave or in a 350º F oven until warmed throughout, about 30 minutes. Spoon the glaze over the sweet potatoes and serve.