For the mashed sweet potatoes: Peel the sweet potatoes and cut into large cubes. Bring a large pot of salted water to a boil, and add the potatoes. Bring it back to a boil over high heat, then simmer for 15-20 minutes, until potatoes are fork tender. Drain the water and allow the sweet potatoes to cool to room temperature. Mash the sweet potatoes with a potato masher or fork.
Preheat oven to 350 degrees. In a large mixing bowl, combine the mashed sweet potatoes, sugar, butter, eggs, vanilla extract, cinnamon, and nutmeg. Mix until well combined.
Add in the cream and mix until well blended.
Spray a 9" x 13" pan with nonstick cooking spray. Pour the sweet potato mixture into pan.
For the pecan topping: In a smaller bowl, mix together the brown sugar, butter, flour, and pecans. Spread the topping over the top of the sweet potato mixture.
Bake for 25 minutes.
Notes
The two pounds of sweet potatoes should yield about 5 cups of mashed sweet potatoes for the recipe. If you prefer a shortcut, you have two options: Use pre-mashed sweet potatoes from the refrigerated section of the grocery store. Or use canned sweet potatoes in light syrup - you will need one 40 ounce and one 15 ounce can. For nutrition purposes, one serving is approximately ½ cup of the casserole.