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 crumble topping.
Bake in the oven for 40 minutes.
Remove and let it cool for 10 minutes.
Serve and enjoy!