Prepare the Sweet Potatoes: Begin by preheating your oven to 350°F (175°C). Place the fresh sweet potatoes in a large bowl, cover with water, and microwave until they are soft enough to mash. Drain the water and mash the sweet potatoes until smooth.
Mix the Ingredients: In a separate small bowl, combine the melted butter, white sugar, maple syrup, vanilla extract, and salt. Pour this mixture into the mashed sweet potatoes, stirring until everything is well combined.
Add the Hash Browns: Gently fold in the hash browns until they are evenly distributed throughout the sweet potato mixture. This step is what gives this casserole its unique twist, adding a savory element that balances the sweetness perfectly.
Assemble the Casserole: Lightly grease a casserole dish with some melted butter or cooking spray. Spread the sweet potato and hash brown mixture evenly into the dish.
Top with Pecans and Marshmallows: Sprinkle the chopped crunchy pecans over the top of the casserole, followed by the mini marshmallows. This combination of toppings will create a golden brown, crispy layer that is both visually appealing and delicious.
Bake: Cover the casserole dish with aluminum foil and bake for 25 minutes. After 25 minutes, remove the aluminum foil and continue baking for an additional 10-15 minutes, or until the top of the casserole is golden brown and the marshmallows are slightly toasted.
Cool and Serve: Once done, remove the casserole from the oven using oven mitts and let it cool slightly before serving. This will help the flavors meld together and make it easier to serve.