How to Make It
Preheat the oven to 400°. Grease a 9-by-13-inch glass or ceramic baking dish with 1 tablespoon of the butter. In a large saucepan of salted boiling water, blanch the sweet potatoes until barely tender, 8 to 10 minutes. Drain well. Spread them in the prepared baking dish in an even layer.
In a small saucepan, melt the remaining 5 tablespoons of butter with the brown sugar. Whisk in the cider and bourbon, season with salt and bring to a boil. Cook over moderately high heat, stirring, until the sugar dissolves, 1 to 2 minutes. Pour the mixture over the sweet potatoes and gently stir to coat.
Bake the sweet potatoes until tender and the sauce is syrupy, 35 to 40 minutes.