Creating an amazing Sweet Potato Casserole is simple when you follow these steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C).
2. Prepare Sweet Potatoes: Peel and chop the sweet potatoes into chunks. Place them in a pot of boiling water and cook until tender (about 15-20 minutes).
3. Mash the Sweet Potatoes: Drain the sweet potatoes and transfer them to a large mixing bowl. Mash until smooth.
4. Mix Base Ingredients: Add granulated sugar, milk, melted butter, eggs, vanilla extract, cinnamon, nutmeg, and salt to the mashed sweet potatoes. Mix until well combined.
5. Transfer to Baking Dish: Pour the sweet potato mixture into a greased 9×13-inch baking dish.
6. Prepare Topping: In a separate bowl, mix brown sugar, flour, softened butter, and chopped nuts until crumbly.
7. Add Topping: Sprinkle the topping mixture evenly over the sweet potato layer. If desired, add mini marshmallows on top for extra sweetness.
8. Bake: Place the casserole in the preheated oven and bake for 30-35 minutes or until the topping is golden brown.
9. Cool: Once baked, remove from the oven and let it cool for 10-15 minutes before serving.