Gratin is one of my favorite things in the world! My mother always made her special version of Scalloped Potatoes (which are quite similar) for Christmas and Thanksgiving and I used to look forward to them every year since we never had them any other time. These days, I love experimenting with different flavors and textures when it comes to gratin… There are so many different combos that can be delicious and rewarding. This cheesy mustard version is one of my new favorites and it's actually a perfect potato option for Thanksgiving and Christmas meals!
Let's talk about ingredients… If you're not sure about finding Gruyere and Emmentaler, substitute 300g of a medium-strength, well-melting Swiss cheese. If you're in the US, it's simply swiss cheese that you're after here - get 300g and grate it, although you could feel free to just substitute more cheddar or another mild, easy-melting cheese of your choice.
If you don't have breadcrumb at the ready, I urge you not to use the sandy ones that you get from the store. Simply get some real bread - not the sliced mushy white stuff used for sandwiches, but something like a crusty roll, a baguette or any fresh white bread from a bakery. Sliced it and dehydrate it in the oven at 200°C for about 15 to 20 minutes. You want it to kind of be the consistency of dry toast, but not too hard, so use your judgement with the timing. Put the slices in the food processor and blitz until you have rough bread crumbs. Personally, I love having these on-hand at all times and tend to make them in bulk. I then keep them in a ziplock back in the freezer for whenever I need them.
Finally, I haven't specified the exact amount of potatoes because it very much depends on how thinly they're sliced, your layering style and the size of the casserole you use. Use what you need and if it helps, I find the slicing tool on a food processor to be a gratin-maker's best friend.
1 tablespoon olive oil
1 cup of fresh or frozen breadcrumbs
1 tablespoon dried thyme
2 teaspoons sea salt flakes
1 teaspoon ground black pepper
300g mild cheddar, grated
180g Gruyere, grated
180g Emmentaler, grated
2 tablespoons plain flour
Approximately 1kg potatoes, sliced very thinly
500g chicken stock
300ml double cream
6 tablespoons Dijon mustard
1. Melt the butter and olive oil together in a frying pan over medium heat and fry the bread crumbs until golden and crispy. If you don't have cup measures handy, just use a coffee cup. Remove to a dish and set aside to cool.
2. Preheat the oven to 200°C and butter one large rectangular oven-proof casserole dish or two medium-sized oval ones. Set aside.
3. Mix the dried thyme, salt and pepper together in a small bowl.
4. Mix the grated cheeses together with the flour, using your hands to toss it and ensure that all of the cheese is coated in the flour. If necessary, add one more tablespoon of flour.
5. Layer potato slices over the bottom of the dish, allowing them to slightly overlap until the bottom of the dish is completely covered. Sprinkle with 1/3 of the salt & pepper mixture and 1/3 of the cheese. Repeat this process two more times until you have 3 layers in total.
5. Stir together the chicken stock, double cream and mustard in a mixing bowl with a wire whisk until well-mixed. Pour the liquid mixture over the potato layers.
6. Bake the potatoes for 30 minutes. Sprinkle the fried breadcrumbs over the top and continue baking until potatoes are tender and fully cooked, approximately another 45 minutes to an hour.
7. Allow the potatoes to stand for 15 minutes before serving, but up to 30 minutes if needed.