Start by preheating your oven to 350°F (175°C). Boil your diced sweet potatoes in a large pot of salted water until they are fork-tender, around 15-20 minutes. This sets the stage for a creamy texture. Once they're tender, drain them and give them a quick cool-off.

In a large bowl, mash the sweet potatoes thoroughly. You can use a potato masher or a hand mixer for an extra creamy finish. The goal is to get rid of lumps to achieve a smooth base for your soufflé.

Once mashed, mix in the dark brown sugar, maple syrup, melted butter, vanilla extract, and nutmeg. This will create a delightful blend of sweetness and flavor. Don’t forget to season with a pinch of sea salt to balance the flavors perfectly.

Next, gently fold in the evaporated milk and beaten eggs. Mix until everything is well combined. This step adds richness and helps bind all the ingredients for a delightful soufflé texture.

Lightly grease your casserole dish with butter to keep the soufflé from sticking. Pour your sweet potato mixture into the dish evenly. Sprinkle the chopped cashews, shredded coconut, and mini marshmallows on top.

Place the casserole dish in the preheated oven and bake for 25-30 minutes, or until the top turns golden and the soufflé is set. Your kitchen will smell heavenly by this time.

After baking, allow the soufflé to sit for a few minutes before serving. This resting period lets it settle. Then, dive into that creamy, sweet goodness topped with crunchy marshmallows and nuts!