Thinly slice the potatoes and season with salt and pepper. Arrange them in a stack in a baking dish.
For the sauce, cook the cauliflower and onion in butter until soft. Add vegetable broth and cream, then blend until smooth. Season with salt, pepper, and nutmeg.
Pour the sauce over the potato stacks and bake at 350°F (175°C) for 45 minutes or until the potatoes are tender.
Garnish with chopped chives before serving.