Potato Leek Gratin

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An epic potato and leek gratin made from sautéed leek, garlic, herbs, milk, cream, agria potatoes and grated cheese. Your new favourite side dish.

A round casserole dish filled with creamy, baked scalloped potatoes, with a serving spoon scooping out a portion. The dish rests on a wooden surface with a cloth nearby.

This Potato Leek Gratin is the kind of dish that always impresses but is actually really simple to make. Sautéing the leeks in butter with garlic and herbs adds so much flavour and a subtle sweetness that works perfectly with the creamy sauce and golden cheese topping. I made this for a family get together and it disappeared in no time. It's a great one when you need to feed a crowd. For another yummy leek recipe, why not try our Chicken and Leek Pie?

Ingredient notes:

Ingredients on a counter: milk, double cream, potatoes, Italian herbs, leeks, shredded cheese, and garlic, arranged in front of a white tiled backsplash.

Potatoes: I like to use a floury potato like agria for this dish. Waxy potatoes may take longer to absorb the liquid and therefore cook though.
Leek: This is a great recipe to use seasonal leek in when it's affordable and plentiful.
Cheese: Any type of grated cheese can be used in this recipe! From a block you already have in the fridge or packaged pre-grated cheese.

Note: Scroll to the recipe card for the ingredients, quantities and the full method.

Step by step instructions:

Preheat the oven to 180°C fan bake.Place a large cast iron ovenproof dish over a medium heat. Add the butter and oil. Once the butter is melted, add the sliced leek. Sauté for 5-10 minutes until starting to soften.

Sliced leeks cooking in a white pan on a stove, with green and white pieces spread out evenly.

Chopped leeks sautéing in oil and herbs in a white frying pan, with browning visible on the pan and some pieces.

While the leek is cooking, peel and thinly slice the potatoes. Sprinkle the Italian herbs over the leek, stir in the crushed garlic and cook for 1-2 minutes until fragrant.

Peeled whole and sliced potatoes are arranged on a wooden cutting board next to a knife with a wooden handle.

Milk is being poured from a measuring cup into a pan of simmering leeks and herbs.

Pour in the milk first, then the cream. Stir together, scraping any brown bits from the base of the dish. Remove from the heat, add the sliced potatoes and gently stir until they are coated in the creamy leek mixture.

Sliced potatoes on a board, grated cheese in a bowl, and a creamy herb mixture with leeks in a casserole dish on a kitchen counter.

Sliced yellow potatoes mixed with chopped green onions, herbs, and a creamy white sauce in a pot, ready to be cooked.

Sprinkle over the grated cheese. Cover with a lid or foil, then place in the oven. Bake for 50 minutes until the potatoes are almost cooked through.

A round baking dish filled with sliced potatoes layered with grated cheese, ready to be baked, sits on a gray countertop.

A baked dish of scalloped potatoes in a creamy sauce sits in a round pan, with a serving spoon partially submerged in the casserole.

Remove the lid or foil and bake for a further 20-30 minutes until the cheese is golden, the potatoes are tender and the sauce has reduced. Leave to sit for 10 minutes before serving.

A close-up of a baked potato gratin with golden, sliced potatoes and creamy sauce in a pan, with a serving spoon scooping some out.

Recipe FAQs:

What should I do if my top is browning too quickly?

Loosely cover it with tin foil, or the lid, while the potatoes finish cooking through.

Why do you sauté the leeks first?

Sautéing the leeks first really brings out their natural sweetness and builds flavour right from the start. Combined with the garlic, herbs and creamy sauce, it gives the whole dish a richer, more balanced taste compared to just layering everything in raw.

How do I know when the potatoes are cooked?

Potatoes can take longer to cook than expected, especially depending on the variety. Make sure they are completely soft before serving by checking with a knife. Waxy potatoes may need a bit longer than floury ones like the agria I used.

Storage:

Store leftovers in an airtight container in the fridge overnight or for up to 3 days. Reheat until piping hot before serving.

Top tips:

Potatoes can take longer to cook than expected, especially depending on the variety. Make sure they are completely soft before serving by checking with a knife. Waxy potatoes may need a bit longer than floury ones like the agria I used.

Related Recipes:

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Potato and Leek Gratin

Yield: Serves 10 as a side

Prep Time: 10 minutes

Cook Time: 1 hour 30 minutes

Additional Time: 10 minutes

Total Time: 1 hour 50 minutes

An epic potato and leek gratin made from sauteéd leek, garlic, herbs, milk, cream, agria potatoes and grated cheese

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Ingredients

1 tsp butter
1 tsp oil
1 leek, finely sliced
1 tsp dried Italian herbs
4 cloves garlic, crushed
2 cups milk
1 cup cream
1.5kg agria potatoes, peeled and thinly sliced
100g cheese, grated

Instructions

Preheat the oven to 180°C fan bake.
Place a large cast iron ovenproof dish over a medium heat. Add the butter and oil.
Once the butter is melted, add the sliced leek. Sauté for 5–10 minutes until starting to soften.
While the leek is cooking, peel and thinly slice the potatoes.
Sprinkle the Italian herbs over the leek, stir in the crushed garlic and cook for 1-2 minutes until fragrant.
Pour in the milk first, then the cream. Stir together, scraping any brown bits from the base of the dish.
Remove from the heat, add the sliced potatoes and gently stir until they are coated in the creamy leek mixture.
Sprinkle over the grated cheese. Cover with a lid or foil, then place in the oven.
Bake for 50 minutes until the potatoes are almost cooked through.
Remove the lid or foil and bake for a further 20-30 minutes until the cheese is golden, the potatoes are tender and the sauce has reduced.
Leave to sit for 10 minutes before serving.

Nutrition Information:

Yield: 10 Serving Size: 1
Amount Per Serving: Calories: 306Total Fat: 14gSaturated Fat: 9gUnsaturated Fat: 6gCholesterol: 43mgSodium: 120mgCarbohydrates: 36gFiber: 4gSugar: 3gProtein: 9g

Nutritional values are approximate. Please use your own calculations if you require a special diet.

Thank you for checking out this recipe. I hope you enjoy making and eating it! If you have any questions, queries or feedback, please feel free to leave a comment below.
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Vanya