Bake the sweet potatoes at 400 degrees F for about 45-50 minutes, or just until fork tender but not mushy. Can be done in advance; can also boil whole until tender. Butter a 9 x 9 inch casserole dish; set aside. Once sweet potatoes are cooled, peel, cut into 1/2 inch rounds and layer into the casserole dish, sprinkling a few light pinches of salt in between the layers.
Preheat the oven to 325 degrees F. Melt half of the butter in a skillet, stirring in the cane syrup and half of the brown sugar until blended. Stir in the cinnamon, cloves, nutmeg and pecans. Remove from the heat and stir in the bourbon. Taste and adjust as needed.
Pour the butter and bourbon mixture on top of the sweet potatoes. Cut the remaining butter into thin slices and spread over the top of the sweet potatoes. Sprinkle the rest of the brown sugar all over the top.
Bake, uncovered at 325 degrees F, basting a few times with a spoon or a baster, for about 25-30 minutes, or until bubbly and thickened.