Pre heat the oven to 350 degrees. Grease a 2 quart casserole dish and set aside.Slice a slit in each sweet potato and cook in the microwave on the potato setting for 10 - 12 minutes or until a knife slides easily into the potato. If you don't want to use a microwave, you can bake the potatoes at 350 degrees for 45 minutes or until very tender. In a small saute pan over medium melt the butter and add the pecans cook until the pecans are golden and the butter is light brown and has a nice nutty aroma. Remove the pecans and drain on a paper towel. Combine the mashed sweet potatoes, the butter and the remaining ingredients except for the pecans in a food processor. If you don't have a food processor you can use a mixer with the whisk attachment. Mix until the potatoes are smooth. Spoon the mixture into a greased 2 quart casserole dish. Bake at 350 degrees, uncovered for 30 minutes or until heated through. Sprinkle pecans on top before serving.
You can make this casserole up to a day ahead. If making ahead, refrigerate the casserole and then bake as directed in the recipe.