Combine canola oil and 1 tablespoon butter in a small bowl.
Lightly grease a 9 x 13 inch baking dish with butter. Place potatoes and brush or drizzle canola oil and butter. Lightly season with salt. Roast potatoes for 15 to 20 minutes or until tender. Remove from the oven.
In a medium bowl, combine egg, butter, cinnamon, sugar and salt. Drizzle egg mixture over potatoes and top with marshmallows. Return to oven and bake for another 15 to 20 minutes or until marshmallows looks lightly brown. Serve
Recipe by The Gluten Free at https://www.theglutenfree.com/g-free-sweet-potato-casserole-with-marshmallows/