Directions

1. Peel potatoes and sweet pota­toes. Cut them into slices ¼-inch (5-mm) thick.
2. Place a piece of parchment paper at the bottom of a 9-inch (2-L) baking dish and cover with half the butter. Arrange a layer of regular potatoes over bottom of dish. Sprinkle pota­toes with a little olive oil, salt, pepper and rosemary. Con­tinue to layer and sprinkle potatoes until you have used half the potatoes.
3. Arrange sweet-potato slices on top, sprinkling with oil, salt, pepper and rosemary after each layer.
4. Continue to arrange remain­ing potatoes in layers on top of sweet potatoes, sprinkling after each layer.
5. Butter another piece of parch­ment paper with remain­ing butter. Place paper, butter-side down, on top of potatoes. Weigh down paper with a heavy oven­proof dish or foil-covered bricks.
6. Bake in a preheated 425°F (220°C) oven for 1 hour, or until potatoes are tender. Remove weights and the top paper. Let pota­toes sit for 5 minutes.
7. Invert dish onto a serving platter and remove remaining piece of parchment paper. Serve with the best-looking side up.

Bonnie says: Potato gratins are often loaded with cream, butter and cheese, but this version is much lighter—and every bit as delicious. It has amazing flavour and, of course, looks absolutely stunning. This recipe is adapted from one by food stylist Olga Truchan.