Begin by preheating your oven to 350°F (175°C). This will ensure that your sweet potato casserole bakes to perfection.

Wash the sweet potatoes thoroughly and peel them.

Cut the sweet potatoes into chunks and place them in a pot of boiling water.

Boil the sweet potato chunks until they are tender, approximately 15-20 minutes.

Drain the cooked sweet potatoes and transfer them to a large mixing bowl.

Use a potato masher to mash the cooked sweet potatoes until they are smooth.

Add the granulated sugar, brown sugar, unsalted butter, eggs, vanilla extract, and milk to the mashed sweet potatoes.

Mix all the ingredients together until well combined.

Transfer the sweet potato mixture to a greased baking dish, spreading it out evenly.

In a separate bowl, combine the all-purpose flour, granulated sugar, chopped pecans, and softened unsalted butter.

Mix until the topping mixture resembles coarse crumbs.

Sprinkle the topping evenly over the sweet potato mixture in the baking dish.

Bake the baking dish in the preheated oven for about 30 minutes, or until the casserole is thoroughly heated through and the top is golden brown.