To make sweet potato casserole ahead of time, prepare the sweet potato mash, and top it with the nut mixture, then cover it and stick it in the fridge for a day. Then when the turkey comes out, set the oven to 350 degrees, remove the cover from the casserole and bake it until the topping is showing the deliciously telltale signs of being roasty toasty and the brown sugar is turning to a crispy sugary candied coating. This takes about 50 minutes when the casserole goes in the cold. Just keep an eye on it, and when the nuts start to brown, you’ll know it’s ready.