Preheat oven to 400 degrees. Prick each sweet potato with a sharp knife. Wrap each tighlty in tin foil. Place potatoes on a baking sheet and place in hot oven. Bake for approximatley 1 hour or until potatoes feel soft when sqeeezed ligthly. Remove from oven and let cool enough to handle. With a paring knife, carefully remove skin of sweet potatoes. It should come off easily by making a slit in the skin along the long side of the potato and cutting the end off. Add the peeled potatoes to the bowl of a stand mixer. Mix at low spped to mash potatoes.
Add next 7 ingredienst (everything except eggs) and beat at low speed until blended and smooth, 1-2 minutes. Add eggs and beat until thoroughly combined, approximately 1 min.
Turn oven back to 375 degrees.
Lightly spray or grease a 3 qt casserole dish. Sppon sweet potato mixture into casserole.
To make struesel topping, combine brown sugar, oats, flour and cinnamon in a medium bowl. Stir to combine. Cut in butter using a fork, pastry cutter or your fingers, until butter is incorporated into pea size pieces. Stir in chopped pecans and combine thoroughly. Distribute streusel topping evenly over sweet poatto mixture. Bake is 375 degree oven for 30-40 minutes or until mixture is bubbling and topping is browned.
Casserole can be made ahead, without baking, and refrigerated for 2-3 days. If baking from cold, increase cooking time to 60-70 minutes.
