Please note that the terms "sweet potatoes" and "yams" are used interchangeably to refer to the same thing.
Preheat the oven to 350 degrees F.
Preparing the Baking Dish - Using a baking or cooking brush, generously grease the inside (bottom and sides) of the baking dish with softened butter. Set aside for a moment.
For the Canned Yams - Strain the canned sweet potatoes in a colander. Some of the cut yams in the can will likely be soft so don't stir the potatoes around. Drain and discard all of the liquid in the canned yams.
For the First Layer of Sweet Potatoes - To the greased baking dish, using a spoon or tongs, start adding the sweet potatoes to the baking dish. If there are any particularly large pieces, cut them in half with a knife.
Add enough of the yams to form a single layer in the bottom of the baking dish. Then, sprinkle half (1/8 teaspoon) of the salt evenly on the yams, drizzle half (1-1/2 tablespoons) of the honey evenly on the yams, and sprinkle half (1/2 teaspoon) of the cinnamon evenly on top of the yams.
Cut the butter into small cubes and add half (2 tablespoons) of them evenly on top of the yams.
To a small bowl, add 1/3 cup of packed brown sugar (light colored), and cut it in half. Sprinkle half of the brown sugar evenly on top of the yams.
Last but not least, top the yams with half (1/4 cup) of the cut walnuts (halves and pieces).
For the Second (Top) Layer of Sweet Potatoes - starting with another layer of the sweet potatoes repeat the same process for the second (top) layer.
Baking Just the Sweet Potato Layers - Cover the baking dish with foil and bake in a preheated oven (350 degrees F.) until the sweet potatoes are heated through (about 20 minutes).
Baking the Sweet Potatoes with Marshmallows - Remove the sweet potatoes from the oven (keep the oven on), set the baking dish onto a cookie sheet or large pizza pan (in case some of the marshmallows come off of the baking dish in the oven), and discard the foil.
Carefully (the baking dish will be hot) add miniature marshmallows on top of the sweet potatoes. Add as many marshmallows as possible to cover the sweet potatoes.
Bake in the oven (at 350 degrees F.) UNCOVERED until the marshmallows turn a light brown color (about 15 minutes).
Serve right away while warm either from the baking dish (with a warning to guests of course that the baking dish is hot) or transfer the candied sweet potatoes to a serving bowl.
If serving from a separate dish or bowl, garnish the candied sweet potatoes with additional walnuts (halves and pieces).