Preheat oven to 375 degrees F (190 degrees C). Grease a 9-inch pie dish.
Lay the puff pastry on top of the prepared pie dish. Trim off any excess pastry.
In a large skillet, melt butter over medium heat. Add sweet potatoes, onion, and thyme. Cook for 10 minutes, or until potatoes are tender. Season with salt and pepper.
Remove the skillet from heat and stir in mascarpone cheese. Spread the mixture into the prepared pie dish.
In a medium bowl, whisk together eggs and cream. Pour the egg mixture over the potato mixture in the pie dish.
Bake for 35 minutes, or until the quiche is golden brown and set in the center. Allow to cool for 10 minutes before serving.
Interesting Facts
Mascarpone is an Italian cheese made from cream and cheese curds.
Quiche can be served hot or cold and makes a great lunch or dinner.
Quiche is a French dish that has been around since the Middle Ages.