Preheat your oven to 350°F (175°C).

Peel and chop the sweet potatoes into chunks, then boil them in a large pot of salted water for 15-20 minutes until tender.

Drain the sweet potatoes and return them to the pot; mash until smooth.

Add sugar, milk, melted butter, vanilla extract, eggs, cinnamon, and salt to the mashed sweet potatoes; mix well until fully combined.

Pour the sweet potato mixture into a greased 9x13-inch baking dish.

Evenly spread the mini marshmallows over the top of the sweet potato mixture.

Bake in the preheated oven for 25-30 minutes, until the marshmallows are golden brown and the casserole is heated through.

Remove from oven and let it cool slightly before serving.