· 2 tablespoons olive oil
· 3 large Spanish onion, peeled and sliced thinly
· 2 cloves garlic, finely chopped
· Salt and freshly ground black pepper
· 4 large potatoes, peeled and sliced thinly
· 3 tablespoons balsamic vinegar
· 1 1/4 cups heavy cream
· 1/4 cup finely chopped fresh parsley
· 1 cup grated Gruyere cheese
Heat oil in a large saute pan over medium heat. Add the onions and cook slowly until caramelized. Add the garlic and balsamic vinegar and cook for 2 minutes.
Preheat oven to 375 degrees F.
Butter a 9-inch baking pan and place a layer of potatoes on the bottom and season with salt and pepper. Spoon 1/5 of the onion mixture over the potatoes and top with 1/4 cup of the heavy cream and a tablespoon of parsley. Repeat to make 5 layers. Sprinkle the cheese over the top of the potatoes. Bake for 50 to 60 minutes, or until the potatoes are soft and the cream has been absorbed.