I make this recipe every year for Thanksgiving and Christmas. I received a recipe about 35 years ago and I tinkered with the topping on it through the years. I enjoy this as a side dish with my holiday meal, but my husband likes to eat it as a dessert.
Cook unpeeled sweet potatoes until tender, by whatever method you prefer (baked, boiled or microwaved). My preference is baked, but any method will work.
Allow sweet potatoes to cool enough to be able to handle them. Remove peels and mash sweet potatoes.
Mix all ingredients well with handheld mixer (the mixer blades will catch and remove strings from the sweet potatoes, so don't scrape the beater blades off, just discard whatever clings to them.)
Pour into a buttered or greased casserole or 9"X13" baking dish.
Bake in pre-heated 375°F. oven for about 35 minutes or just until knife inserted in center comes out clean.
While sweet potatoes are baking, prepare topping. Combine brown sugar, chopped pecans, flour and oatmeal. Cut butter into pats, drop on top of other ingredients and then cut butter in with a pastry blender until mixture becomes coarse crumbles. (If you prefer, you can melt the butter and just mix it in, it does give a different texture to the topping but it is still quite acceptable.
Remove from oven, sprinkle topping evenly over sweet potatoes and return to the oven for an additional 10 minutes.