This creamy, indulgent potato, leek and shallot gratin is inspired by an old Epicurious recipe from 2009, which in itself I believe was inspired by a much older recipe; I didn’t have enough leeks for the original recipe, so I subbed in some shallots I had kicking around. I also reduced the yield, as my spouse and I really didn’t want to be eating gratin at every meal for the next week. This should be enough for a meal, seconds if you’re brave, and some leftovers for another day, as it’s very rich and you don’t need much to fill you. This also works very well as a single-skillet recipe; cook the leeks in a large, oven-safe, cast-iron skillet and use the same pan to build the gratin; this means you won’t have to clean another dish (just work carefully with the hot skillet!)

You can add buttered breadcrumbs to the top for a nice toasty crunch, but I didn’t bother, figuring it was just gilding the lily at that point. You can also make this recipe gluten-free by subbing out the flour for half as much cornstarch. I haven’t tried this recipe using dairy-free substitutions, but considering how much cream and cheese is in it, I also don’t want to attempt it as it would be a completely different dish at that point. The same for reducing cholesterol or salt (hellno). This recipe is an unapologetic, no holds-barred trip down memory lane to the rich, unctuous, “company-fancy” casseroles of the 60’s and 70’s; it is what it is — DECIDEDLY NOT diet food — and occasionally you just have to treat yourself, your family, or guests to something awesome.

Potato, Leek and Shallot Gratin

YIELD: 6 svgs | PREP: 10 mins | COOK: 15 mins | BAKE: 35-45 mins | REST: 10 mins

• 1 tbsp/15g salted butter
• 1 tbsp/15mL olive oil
• 3 medium size leeks (white and light green parts only), trimmed, halved lengthwise, thoroughly washed, and thinly sliced
• ¼ cup/60mL water
• 3 shallots, peeled and thinly sliced
• 4-5 large yellow-flesh potatoes
• 2 tbsp/16g flour
• 1½ cups/355mL table cream, or 1 cup/240mL heavy cream plus ½ cup water
• 1 cup/250mL vegetable stock, heated
• 2 stalks fresh thyme (or 2 tsp/3g dried thyme leaves)
• Salt and freshly cracked black pepper to taste
• 1 cup/100g freshly grated Parmesan
• ½ cup/~100g freshly grated Gruyere or your favourite sharp, strong cheese (this works well with blue cheese like Roquefort, or a Manchego or even white cheddar)

1. Preheat oven to 400° F/175° C and place rack in middle of oven. Melt butter and add oil over medium heat to a large (12-inch), heavy-bottomed skillet; cast-iron is best.
2. Add leeks and water to pan, and season with salt and pepper, cooking over medium heat 5 minutes. Add shallots and continue to cook until leeks and shallots are tender but not brown, stirring occasionally (about 8-10 minutes). Lower heat to medium-low.
3. Meanwhile, wash, peel and slice potatoes into identically-sized width “coins” (1/16″). A mandolin cutter works best for this, but if you have good knife skills, that will do fine. Do not submerge cut slices in water, as you want to use the starch that is naturally present in the freshly-cut potatoes (to avoid them turning brown due to oxidization, do not do this step too far in advance).
4. Add the flour to the pan with the cooked leeks and shallots; stir until well-combined and let cook out for a few minutes to remove the raw flour taste. Add table cream, water and warmed vegetable stock; using a whisk, mix well together and increase heat back to medium. Continue to stir with a wooden spoon or silicone spatula until thickened.
5. Butter bottom and sides of a casserole dish; if using skillet, skip this step but don’t bother washing out the skillet (pour leek and shallot sauce into large measuring jug or bowl).
6. Arrange one layer of potatoes across bottom (if potatoes thinly sliced by mandolin, then arrange a double layer). Cover with 1/3 of the leek and shallot sauce, then 1/3 of the two cheeses; salt and pepper each layer to taste. Repeat two more times, until all of your ingredients have been used up or your baking vessel of choice is full.
7. Place dish or pan on a baking tray in order to catch any accidental drips, cover with lid or foil, and bake in hot oven for 35-45 minutes, rotating once halfway through and removing lid at that time.
8. Remove from oven and let rest for 10 minutes before serving.

This is a great make-ahead recipe; you can assemble and chill right up to just before baking, up to 48 hours in advance. Keeps well, covered and refrigerated, for 3-5 days, if it lasts that long!