Sweet Potato Casserole

For the sweet potato base:
2-1/2 lb of sweet potatoes cooked at 350 for about 1 and half hour, or until tender
2 Eggs
1/4 cup of Granulated Sugar
1/4 cup Whole Milk
1/4 cup of Brown Sugar
1/4 cup of Unsalted Butter softened at room temperature
1/2 tsp Salt

For the Topping:
1/4 cup of Brown Sugar
2 Tbsp of Flour
1-1/2 Tbsp of Unsalted Butter cold and cut into cubes
1/2 cup of Chopped Pecans
About 1 to 1-½ cups of Marshmallows