Bake sweet potatoes. Preheat oven to 375°F. Line a baking sheet with aluminum foil for easy cleanup. Place washed sweet potatoes on baking sheet. Bake for 45 minutes to 1 hour, depending on size of potatoes. Potatoes are done when they feel soft when squeezed and a fork can easily be inserted to the center. Remove from oven and let cool slightly.
Mash sweet potatoes. Once potatoes are cool enough to handle, remove skins from baked sweet potatoes, discard any stringy pieces. Mash sweet potatoes until flesh is smooth using a potato ricer, a hand masher or with an electric mixer.
In a large mixing bowl, combine mashed sweet potatoes, butter, and sugar. Mix until smooth. Stir in eggs, vanilla extract, salt and milk. Mix on low until eggs and milk are combined. Transfer sweet potato mixture to a 9 X 13 – inch casserole dish. Preheat oven to 350°F.
To make the streusel topping: In a medium bowl, whisk together brown sugar and flour. Pour in the melted butter and stir until the mixture looks crumbly. Add oats and coconut flakes, mixing until everything is evenly coated. Sprinkle streusel topping evenly over sweet potatoes.
Bake sweet potato casserole in preheated oven for 40-45 minutes or until streusel topping is golden brown. Remove from oven and serve casserole warm.
Notes
Notes: Recipe uses approximately 6 cups of mashed, cooked sweet potatoesPecan Streusel Topping: Omit oats and coconut add 1 cup chopped pecans to streusel mixture.