For the sweet potatoes: Preheat the oven to 375 degrees F.
Bake the sweet potatoes until fork-tender, 30 to 35 minutes. Remove the potatoes and raise the oven temperature to 400 degrees F.
Slice the sweet potatoes in half and let them cool slightly. Scoop out the innards, place into a large bowl and give them a good mash, leaving some texture to the potatoes--no need to mash completely. Add the granulated sugar, milk, salt, vanilla extract and eggs. Stir and mash the mixture around--you don't want them to be perfectly smooth.
Butter a 2-quart baking dish, pour in the potatoes and smooth out the top.
For the topping: Combine the brown sugar and flour in a bowl. Throw in the butter and with a pastry cutter, cut together until thoroughly combined. Add the pecans and combine until the topping is nice and crumbly. Sprinkle the crumb mixture all over the top of the potatoes.