Boil cassava, dasheen, sweet potato, and plantain whole with skin on in salted water until fork-tender. Remove each as it finishes cooking.
Let cool slightly, peel, remove cassava core, and cube.
Add provisions to a large bowl with onion and pimento peppers.
In a separate bowl, whisk milk, egg, butter, salt, and black pepper.
Pour liquid over provisions and mix gently.
Fold in most of the cheese, reserving some for topping.
Transfer to a greased baking dish.
Top with remaining cheese.
Bake at 350°F for 30 to 35 minutes.
Broil for 3 to 5 minutes until golden.
Rest for 10 minutes before serving.