Bacon & Leek Potato Gratin

close up overhead shot of black spatula lifting portion of leek bacon potato gratin

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5 from 3 votes

Easy cheesy potato gratin loaded with bacon and leeks. This truly is the ultimate side dish!

Prep Time15

Cook Time1 15

Total Time1 30

Course: Side Dish

Cuisine: French

Servings:

Author: Chris Collins

Cost: £1.50 / $2

Equipment

9" x 9" Baking Dish (or similar size)
Small/Medium Pot & Wooden Spoon
Vegetable Peeler
Sharp Knife & Chopping Board
Cheese Grater
Brush (optional)

Ingredients

2lb / 1kg Maris Pipers/Russets (or other starchy/baking potato)
1lb / 500g Leeks, trimmed & finely diced (weight of whole leeks BEFORE trimmed)
7oz / 200g Bacon, finely diced (smoked or unsmoked, can also sub pancetta)
2 cups / 200g Gruyere, grated and divided into two portions (1 cup for the layers, 1 cup to finish on top
1 1/4 cups / 300ml Double/Heavy Cream
1 1/4 cups / 300ml Whole Milk (don't sub skimmed or semi-skimmed)
1/2 tbsp Butter
3/4 tsp Salt
1/4 tsp EACH: Ground Nutmeg, Black Pepper

Instructions

In a medium-sized pot over low-medium heat fry bacon until crisp with the fat rendered. Discard most of the fat, leaving a little behind to fry the leeks. Raise heat to medium, then add in leeks and continue frying until soft. Remove everything from the pot and place to one side.
Pour milk and cream into the pot then add salt, pepper and nutmeg. Bring to a very gentle simmer and allow to infuse for 5 or so mins, just until it starts to thicken. Don't allow it to rapidly bubble or foam, this risks the liquid curdling.
Meanwhile, peel and slice your potatoes into very thin rounds (approx 3-4mm or 1/8"). I find this easiest by slicing a thin layer off the base of the potato to stabilize it when cutting. You can also use a mandoline.
Rub a 9x9" baking dish with butter, then pour in a splash of cream and spread over the base (I find this easiest using a brush). Add a layer of potatoes, overlapping slightly as needed to prevent gaps. Pour over a layer of cream and brush to cover the potatoes, then sprinkle over some of the bacon/leek mix and top with a layer of gruyere. Continue the layers finishing with potatoes and a layer of cream on top (remember to save half of the gruyere to top). For reference, you should end up with 5 potato layers and 4 cheese/bacon/leek layers.
Place in the oven at 170C/340F for 1 hour, or until knife tender and lightly browned on the top. This may take slightly longer or less time depending on the depth of your dish, so just be vigilant (see notes).
Take the dish out and sprinkle with gruyere. Pop back under the grill and broil for a couple of mins until golden and crispy. Allow to rest for a few mins so the potatoes retain shape, then slice into portions and enjoy!

Video

Notes

a) Leeks - Ensure you trim off the dark green leaves (you can save these for stocks or soups; they're too tough to eat normally). From there I recommend slicing in half and checking for dirt before finely dicing (rinse in cold water if you see any).

b) Gruyere - This is by far the best cheese to use here. It's got a gorgeous sweet and nutty flavour, which gets enhanced so beautifully with the nutmeg. Second choice is cheddar but definitely use gruyere if you can.

c) Temp/Timings - You want to be on the safe side and bake for a longer time at a lower temp, just to full ensure the potatoes cook right through. This also ensures the cream doesn't split (happens if oven temp is too high). Ovens are all slightly different too, so timings will vary slightly. If you find after around 45mins the potatoes are struggling to cook through then increase the temp slightly to 180C/350F. On the contrary if you find the top is browning too quickly and the potatoes are too firm, just drop the temp slightly to 160C/320F.

d) Storage - I do like to make these fresh, but you can make them ahead of time if you'd prefer. The potato just soaks up a fair bit of the cream as they rest and they don't come out quite as saucy. Still taste awesome though! Just cook as instructed then allow to completely cool and tightly store in the fridge for 3-4days. Cover in foil and reheat in the oven at 180C/350F for 30mins, or until bubbling hot through the centre. Can grill/broil the top again to crisp up if you want! Can reheat individual portions in the microwave for ease if you'd prefer.

e) Calories - Whole recipe divided by 6.

Nutrition