Step 1: Cook the Sweet Potatoes: Peel and chop sweet potatoes into chunks. Boil in salted water for 15–20 minutes, or until tender. Drain well.
Step 2: Mash and Mix: In a large bowl, mash the sweet potatoes until smooth. Add butter, sugars, evaporated milk, egg, spices, vanilla, and salt. Mix until creamy and fully combined.
Step 3: Prepare the Dish: Preheat oven to 350°F (175°C). Lightly grease a small baking dish (about 8x8 inches). Pour in the sweet potato mixture and smooth the top.
Step 4: Add the Topping: In a small bowl, mix pecans, brown sugar, flour, and melted butter. Sprinkle evenly over the sweet potato layer.
Step 5: Bake and Add Marshmallows: Bake for 20 minutes. Remove, top with mini marshmallows, and return to oven for another 8–10 minutes, or until the marshmallows turn golden brown and slightly toasted.