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Golden leek gratin and homemade mashed potatoes with a breadcrumb crust, in two baking dishes on a green table

Leek Gratin with Homemade Baked Mashed Potatoes

Main dishes

Tender leek gratin under a Gruyère béchamel, served with homemade mashed potatoes baked with a breadcrumb crust: true winter comfort food.

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A leek gratin that melts under a golden Gruyère béchamel, and alongside it homemade mashed potatoes that also go into the oven, with a crust of breadcrumbs and cheese. That night, the verdict around the table was unanimous: it was delicious!

The secret is to drain the leeks well after cooking: they release a lot of water, and that's what makes the difference between a creamy gratin and a watery one. The mashed potatoes are made with real potatoes, butter and hot milk, then baked at the same time as the leeks.

Two simple, inexpensive seasonal dishes that you make side by side and that come out of the oven together.

Ingredients and directions

  • Prep time25 min
  • Cook time45 min
  • Total1 hr 10 min
  • DifficultyEasy
  • CostBudget
  • Calories734 kcal/serving
  • Cooking methodBaked
  • Estimated cost$9.09 $2.27 / serving Estimated price; varies by store. Converted from euros at the ECB rate of September 25, 2026.
  • Vegetarian

Ingredients

4 servings

Leek gratin

  • $2.28
  • $0.23

Béchamel

  • $0.46
  • $0.06
  • $0.63
  • $0.06
  • $1.82

Baked mashed potatoes

  • $1.71
  • $0.25
  • $0.46
  • $0.17
  • $0.91
  • $0.06

Directions

Mashed potatoes

  1. Peel the potatoes, cut them into chunks and cook them for 20 to 25 minutes in a large pot of cold salted water brought to a boil.
  2. Drain, mash with the butter using a potato masher, then add the hot milk a little at a time. Season with salt and pepper and spread in a buttered baking dish.

Leeks

  1. Preheat the oven to 200 °C. Cut the leeks into 3 cm pieces and rinse them well to remove any grit.
  2. Cook them gently for 15 minutes in a sauté pan with 20 g of butter and a splash of water, covered, then drain them thoroughly, pressing out the liquid.

Béchamel and baking

  1. Melt the butter in a saucepan, add the flour and stir for 1 minute without letting it brown.
  2. Pour in the cold milk while whisking and cook until thickened. Season with salt, pepper and nutmeg, and stir in half the Gruyère.
  3. Arrange the leeks in a second baking dish and cover them with the béchamel. Sprinkle with the rest of the Gruyère.
  4. Top the mashed potatoes with breadcrumbs and grated Gruyère.
  5. Bake both dishes for 20 minutes, until the tops are nicely golden. Serve piping hot.

The bill

Leek Gratin with Homemade Baked Mashed Potatoes

  • 4 leeks (about 800 g)$2.28
  • 20 g butter for cooking$0.23
  • 40 g butter$0.46
  • 40 g flour$0.06
  • 50 cl milk$0.63
  • 1 pinch nutmeg$0.06
  • 100 g grated Gruyère$1.82
  • 1 kg mashing potatoes (such as Bintje)$1.71
  • 20 cl hot milk$0.25
  • 40 g butter$0.46
  • 30 g breadcrumbs$0.17
  • 50 g grated Gruyère$0.91
  • Salt and pepper$0.06

Total$9.09

that's $2.27 per person

Estimated price; varies by store.

Equipment

  • Two baking dishes
  • Sauté pan
  • Saucepan
  • Potato masher
  • Whisk

Nutrition per 1 plate (leeks and mashed potatoes)

Calories734 kcal
Fat36.3 g
Saturated fat23.2 g
Carbohydrates73 g
Sugars17.1 g
Fiber10.2 g
Protein26.3 g
Salt1.37 g

Before you start

Ingredients

  • 4 leeks (about 800 g)
  • 20 g butter for cooking
  • 40 g butter
  • 40 g flour
  • 50 cl milk
  • 1 pinch nutmeg
  • 100 g grated Gruyère
  • 1 kg mashing potatoes (such as Bintje)
  • 20 cl hot milk
  • 40 g butter
  • 30 g breadcrumbs
  • 50 g grated Gruyère
  • Salt and pepper

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