Preheat oven to 350°F.
In a bowl, mix together goat cheese and heavy cream until smooth. Season with salt and pepper, then stir in chopped chives. Set aside.
Using a mandoline or sharp knife, slice potatoes into 1/8-inch thick slices. Rinse and keep in cold water.
In a large skillet, heat olive oil and sauté onions with minced garlic for about 10 minutes until caramelized. Season with salt and pepper.
Drain potatoes and pat completely dry with paper towels.
In an ovenproof dish, layer half the potato slices in overlapping rows.
Cover with half the caramelized onions and 1/4 of the goat cheese mixture.
Repeat layering with remaining potatoes, onions, and another 1/4 of cheese mixture.
Top with remaining goat cheese mixture and pour any leftover cream over the top.
Dot surface with cubed butter and season final layer with salt and pepper.
Bake for 1 hour until golden brown and potatoes are tender when pierced with a knife.