Preheat your oven to 375°F (190°C) and grease your baking dish with cooking spray or butter.

Peel and slice the sweet potatoes into thin rounds. Boil in salted water for 10-15 minutes until tender, then drain.

Layer half of the sweet potato slices at the bottom of the greased baking dish.

Sprinkle half of the fresh cranberries over the first layer of sweet potatoes.

In a mixing bowl, whisk together heavy cream, brown sugar, cinnamon, salt, and pepper until sugar dissolves. Pour half over the layers.

Repeat layering with remaining sweet potatoes, cranberries, and pour the remaining cream mixture on top.

Sprinkle Gruyère cheese and breadcrumbs evenly over the top.

Bake for 30-35 minutes until the top is golden brown and bubbly.

Let the gratin cool for 10 minutes, then serve.