I found this on http://southernfood.about.com/ a few years back. Now I am asked to make it every year for both Christmas & Thanksgiving. The picture is also from the website, not mine, but from the oven recipe.

2 cans (18oz) sweet potatoes, drained and mashed (or fresh cooked sweet potatoes)
1/4 cup butter, melted
2 tablespoons sugar
2 tablespoons light brown sugar, packed
1 tablespoon orange juice
2 eggs, beaten
1/2 cup milk
1/2 cup chopped pecans
1/2 cup light brown sugar, packed
2 tablespoons flour
2 tablespoons butter, melted
I also throw on some mini marshmallows right before serving.

Lightly butter the crock pot. Mix mashed sweet potatoes, butter, 2 tablespoons granulated sugar, and 2 tablespoons brown sugar together in a large bowl. Beat in juice, eggs, and milk. Transfer to the crock pot.
Combine pecans, brown sugar, flour, and 2 tablespoons butter. Spread evenly over the top of the sweet potatoes. Cover and cook on high for 3 to 4 hours.
Serves about 6.