Bake for 45 minutes to an hour or until fork tender. Leave the oven on to bake the casserole.
Slice baked sweet potatoes in half and scoop out the puree into a large bowl.
Add remaining ingredients and mix very well.
Pour in a 10 inch cast iron skillet or 9 inch baking dish.
Making sourdough topping
In a bowl add all the ingredients and mix well to combine.
Assemble the casserole
Pour the sourdough topping over the sweet potato mixture.
Spread evenly or swirl into mixture with a butter knife.
Bake the casserole
Bake for 20-25 minutes or until the topping is lightly golden brown.
Notes
Store in an airtight container in the fridge for 3-4 days.Variations:Roast cubed sweet potatoes in 350 degree F oven until for tender. Mix all ingredients and proceed as noted above for a chunkier casserole.