Directions

Preheat oven to 325 degrees F. Butter the sides and bottom of a 10” x 7” inch oval baking dish.

Using a mortar and pestle, grind 1 teaspoon of the mustard seeds into a very coarse powder. Set aside.

In a saucepan, combine sliced potatoes, garlic, milk and water. Bring the mixture to a boil, then reduce the liquid to a simmer. Cook about 5 minutes until the potatoes begin to soften. Drain the potatoes, saving 1-cup of liquid. Set potatoes aside.

Combine the reserved cooking liquid with the cream. Whisk in the dijon mustard and the roughly ground mustard seeds. Season with salt and white pepper. Layer the potatoes in the baking dish, sprinkling flour and some of the cheese between each layer. Reserve half of the cheese for the top. Pour the mustard cream mixture over the potatoes until it comes about halfway up the side of the dish. Sprinkle the top with the remaining cheese and distribute the mustard seeds evenly across the cheese.

Place the baking dish on a cookie sheet to catch anything that may bubble over. Bake at 325 degrees F for 25 minutes. Then place it under a broiler for a few minutes. Watch it closely, and turn the pan often to assure a good even brown crunchy crust. Let the gratin rest about 5 minutes before serving.