Peel and slice sweet potatoes into smaller pieces (~2 inches long).
Bring water to boil in a large pot, then add sliced sweet potatoes into water. Cook for 20 minutes, or until sweet potatoes are soft.
When potatoes are done, drain water, and mashed potatoes with a potato masher or electric mixer until there are no lumps and smooth.
Let potatoes cool.
While waiting, combine all the crumble ingredients in a bowl.
Pre-heat oven to 400 ℉.
Once sweet potatoes are cool, add eggs, brown sugar, vanilla extract and 1/4 cup of unsalted butter. Mix well using a spatula or electric mixer to combine.
Bring sweet potato filling to a 9" x 13" rectangular or 12" oval casserole dish, then evenly top with pecan topping.
Bake in the oven for 40 minutes.
Remove and let it cool for 10 minutes.
Serve and enjoy!