- Toss together the cheese and cornstarch in a large bowl to coat.
- Bring the cider and vinegar just to simmer in a medium saucepan over medium heat. Reduce the heat so that the mixture barely simmers. Add a handful of cheese and stir until smooth. Add the remaining cheese a handful at a time, stirring until smooth between additions.
- Increase the heat to medium and cook until fondue begins to bubble, stirring constantly. If the mixture persists in being lumpy, increase the heat a bit and keep stirring.
- Stir in the Calvados. Season with salt and pepper.
- Transfer to the fondue pot and sprinkle with nutmeg. Serve warm with the accompaniments of your choice.