Preheat oven to 350.
Open and drain canned sweet potatoes or bake and peel sweet potatoes
Mash sweet potatoes until there are no lumps and enough for 3 cups.
Cream butter and sugar.
Add eggs and vanilla then add potato mash.
Pour into buttered casserole dish and bake 40 minutes.
For topping, melt butter and then blend all ingredients and spread over casserole after 40 minutes.
Heat until brown sugar melts and is bubbly but do not burn.