Dinner · Fall · Vegetarian · Baking

Leek, Potato and White Bean Gratin with Thyme

Name: Leek, Potato and White Bean Gratin with Thyme
Prep time: 20 min
Cook time: 55 min
Total time: 85 min
Yield: 4 dinner portions
Ingredients: 750 g yellow-fleshed potatoes, peeled and sliced about 5 mm thick; 2 medium leeks, white and light-green parts only, halved, washed and thinly sliced, about 2 cups prepared; 1 tbsp olive oil; 2 garlic cloves, finely chopped; 1 tsp fresh thyme leaves, or 1/3 teaspoon dried thyme; 300 mL lower-sodium vegetable broth, plus a splash if needed; 1 tsp Dijon mustard; ¼ tsp fine salt; ¼ tsp ground black pepper; 1 540 mL can cannellini or other plain cooked white beans, drained and rinsed, about 325 g drained; 1 tsp butter, for the baking dish; ¾ cup shredded vegetarian-suitable old cheddar, about 75 g

Thin potatoes and cleaned leeks simmer in vegetable broth, then bake with ready-cooked white beans and a cheddar top. Four vegetarian dinner portions without cream or bacon.

Edited by Tasty Recipes editorial team

Published 2026-09-24

1 hr 25 minMakes 4 dinner portions

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How to make Leek, Potato and White Bean Gratin with Thyme

Timing breakdown · 6 timed stages

Estimated total: about 20 minutes to clean and slice, 20 to 25 minutes on the stovetop, 25 to 30 minutes in the oven and a 10-minute rest. Potato thickness and baking-dish depth affect timing; check the centre with a knife.

Preparation: 20 min
Cooking: 55 min

Cooking Step 2: 6 to 8 minutes
Preparation / waiting Step 2: 30 seconds
Cooking Step 3: 10 to 12 minutes
Baking Step 4: 15 minutes
Baking Step 5: 12 to 15 minutes
Resting / cooling Step 5: 10 minutes

Durations are taken from the method and may overlap. Some preparation steps are not timed. Optional stages are separate from the main meal.

01
Heat the oven to 200°C (400°F). Butter a shallow 2 L baking dish. Halve the leeks lengthwise, separate the layers and rinse away grit; drain and slice the white and light-green parts. Peel and slice the potatoes evenly to about 5 mm thick.
02
Heat the olive oil in a large lidded saucepan over medium heat. Add the leeks and cook, stirring, for 6 to 8 minutes until softened without browning. Stir in the garlic and thyme for 30 seconds.
03
Add the sliced potatoes, broth, Dijon mustard, salt and pepper. Stir gently to distribute the leeks. Cover, bring to a gentle simmer and cook for about 10 to 12 minutes, turning the slices once or twice, until a knife enters a centre slice with slight resistance and the pieces still hold their shape. Add a small splash of broth if the pan dries before the potatoes soften.
04
Drain and rinse the cooked beans. Fold them gently through the potato mixture so they are distributed without mashing. Transfer the potatoes, leeks, beans and all remaining cooking liquid to the prepared dish. Spread evenly, cover tightly with foil and bake for 15 minutes.
05
Remove the foil, scatter the cheddar evenly over the surface and bake for another 12 to 15 minutes, until the cheese is golden, the liquid is bubbling and a knife slides easily through potatoes at the centre. If the top colours before the middle is tender, cover loosely and continue baking. Rest for 10 minutes before serving four dinner portions.
06
For leftovers, refrigerate in shallow containers within 2 hours. Eat within 2 to 3 days. Reheat a portion to 74°C (165°F) using a food thermometer; discard uneaten leftovers after reheating.

Recipe questions

Why wash between the leek layers?

Soil can hide inside the tightly packed layers. Halve the leeks lengthwise, fan the layers under running water, then drain before slicing.

Can I use dried thyme?

Yes. Use 1/3 teaspoon dried thyme in place of the 1 teaspoon fresh leaves. Add it with the garlic so it hydrates before the potatoes simmer.

Can I use a different cheese?

A vegetarian-suitable Gruyère-style cheese can replace the cheddar by weight. Check the label for the rennet used if you need a vegetarian meal. The potatoes still need the same centre-tenderness check.

Can I use a different cooked bean?

Plain cooked navy beans can replace cannellini beans at about the same drained weight. Drain and rinse them; do not use uncooked dry beans in the baking dish.

Is this the same as potato leek soup?

No. The cooked white beans make this a four-portion baked dinner with a golden cheese top. Our potato leek soup is blended with cream and served in bowls.

Cooking & storage

Use the recipe’s specific storage directions when provided. Read the food storage guide for chilling and reheating food, and the measures guide before changing portions or ingredients.

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Recipe source: Adapted from Foodland Ontario: Herb Potato Gratin. This version adds ready-cooked white beans to turn the potato-leek side into a four-portion dinner, uses Dijon and a simpler thyme seasoning, and keeps the broth-baked method. Timing is estimated; The dish image is an editorial illustration.

Additional references: Health Canada: food safety tips for leftovers