Boil the Sweet Potatoes: Place unpeeled sweet potatoes in a large pot and cover with water. Bring to a boil and cook for 30-40 minutes until the potatoes are fork-tender. The potatoes should be soft enough that a fork easily slides into the flesh.
Cool and Drain: Drain the cooked potatoes and cool them under running water until they're comfortable to handle. This makes removing the skins much easier and prevents burning your hands.
Preheat the Oven: Heat your oven to 350°F (175°C). This moderate temperature will allow the casserole to heat through evenly without burning the edges.
Prepare the Potatoes: Cut the cooled potatoes into manageable pieces and remove the skins. The skins should slip off easily after boiling.
Create the Base Mixture: In a large bowl, combine the peeled potatoes, butter, salt, and orange juice. Mix until fluffy using a hand mixer or potato masher. The orange juice adds a subtle citrus flavor that complements the sweetness of the potatoes.
Add Pineapple: Gently fold in the drained crushed pineapple until evenly distributed throughout the sweet potato mixture. The pineapple adds a tropical sweetness and interesting texture contrast.
Transfer to Baking Dish: Spread the mixture evenly into a greased 9x13 inch baking pan. Ensure the surface is level for even cooking and presentation.
Initial Bake: Bake the casserole for 20 minutes at 350°F. This allows the flavors to meld together and the mixture to heat through completely.
Add Marshmallow Topping: Remove the casserole from the oven and evenly distribute the mini marshmallows across the top of the sweet potato mixture, covering the entire surface.
Final Bake: Return the casserole to the oven and bake for an additional 5-10 minutes, until the marshmallows puff up and turn a beautiful golden brown. Watch carefully during this step to prevent burning.
Serve: Remove from the oven and serve hot as a delicious side dish.
