Begin by peeling and cubing the sweet potatoes. Aim for uniform sizes to ensure even cooking.
Place the cubed sweet potatoes in a large pot and fill it with enough water to cover the potatoes by at least an inch.
Bring the water to a boil over high heat. Once boiling, reduce the heat to medium and simmer for about 20 minutes, or until the sweet potatoes are tender and easily pierced with a fork.
Drain the cooked sweet potatoes in a colander and return them to the pot.
Add the butter, milk, salt, black pepper, and ground cinnamon (if using) to the potatoes.
Mash the sweet potatoes using a potato masher or hand mixer until smooth and creamy. Adjust the consistency by adding more milk if needed.
Taste and adjust seasoning, adding maple syrup for extra sweetness if desired.
Transfer the mashed sweet potatoes to a serving bowl and serve warm.