Preheat oven to 350℉.
Peel then slice the sweet potatoes between 1/4-1/2 inch thick. Doesn't have to be perfect. Once sliced, add them into the baking dish.
Now, grab a pot and add the butter. Melt the butter on a medium heat. Mix the cornstarch with the sugar before going to the next step. Next, stir in the sugar, brown sugar, vanilla extract, spices and salt. Once melted turn off the heat. Mix in the heavy cream.
Pour the mixture from the pot over the sweet potatoes. Cover the baking dish with foil then place in the oven for 45 minutes.
Remove the foil then bake a remaining 25-30 minutes. The candied sweet potatoes will be soft and tender at this point. Remove from the oven and allow to cool.
Lastly, after 20 minutes of cooling, the sauce will have thickened up and the sweet potatoes are cool enough to serve, enjoy!