Katie Brown | Potato Gratin

Ingredients

• 6 all purpose potatoes, sliced thin on the flat side of a box grater
• 1 tablespoon butter, plus extra for the pie dish
• 1 yellow onion, chopped
• 1 1/2 cups grated parmesan cheese
• 1/4 cup roughly chopped chives
• 1 cup heavy cream
• Salt