In a bowl, mix together the goat cheese with the cream. Season with salt and pepper. Add in the chives. Keep aside.
Preheat the oven to 350 degrees F. Slice the potatoes into 1/8-inch thick slices by using a mandoline or a very sharp knife. Rinse and keep in cold water.
In a large skillet, saute the onions with garlic for about 10 minutes in olive oil. Season with salt and pepper.
Drain and pat dry the potatoes. In an ovenproof dish, nicely layer the potato slices. Cover with some caramelized onions, and 1/4 of the goat cheese mixture. Repeat the layers and finish with the goat cheese mixture. Season each layer with salt and pepper. Pour the rest of the cream mixture over the potatoes and the butter. Cook in the oven for 1 hour until golden brown.