This creamy, cheesy potato and leek gratin is the ultimate comfort food. This gorgeous potato side dish contains thinly sliced potatoes baked in a rich cheesy cream sauce with buttery leeks, finished with the most delicious golden crust. Ready in just under an hour!

I’ve made no secret that I love potatoes on here, and this recipe is no different: the combination of cheese, potatoes, and leeks are the peak of winter comfort food, in my eyes. Other potato recipes you have all loved recently include these super crispy roast potatoes, this very similar scalloped potatoes recipe, my Greek potatoes with whipped feta, and these epic cajun fries (like a homemade Five Guys fry!)

How To Make This Potato and Leek Gratin

I’ve included the exact recipe with the ingredient quantities and instructions in the recipe card below, but here is a quick overview.

Step 1) Prepping your ingredients

Slicing your leeks and potatoes is one of the most time-consuming parts of this dish, so I like to do this first. Cut the ends off your leek, then halve it down the middle lengthways before slicing thinly.

For your potatoes, wash them and peel them, then slice thinly. You could either use a mandolin to help you slice your potatoes nice and thin, or you could just use a knife and chopping board with extra case! (I slice my potatoes with my knife as I don’t own a mandolin. Just take care the potato doesn’t slip and put your fingers at risk!!)

Step 1) Saute your leeks

Start by sauteing your leeks in butter until they’re soft and fragrant, then add minced garlic to your pan.

Step 2) Make the creamy sauce

To make the cream sauce, we add white wine to the leeks, then pour in double cream, seasonings, and three-quarters of the extra-mature cheddar cheese. Reserve the remaining cheese to sprinkle over the top of the dish!

Step 3) Arrange the potatoes

Pour a spoonful of the leek mixture into the bottom of your baking dish, and then arrange your potatoes. I like to arrange them stacked upright to get more of the edges really lovely and crispy in the oven. I also think this looks a little more extravagant, but it’s not essential.

Step 4) Pour over the sauce

Pour your creamy leek sauce all over the potatoes, using your spatula to gently help ease the cream and leeks in the gaps between the potatoes if you can.

Step 5) Bake!

Scatter over the remaining cheese, and then bake the dish covered with foil for 30 minutes, followed by 20 minutes without. The top should be beautifully golden and crispy and bubbly when you remove it from the oven!