Moist Leek Gruyere Tart

This moist and savory leek tart with Gruyere and onions is the kind of recipe that gets requested over and over in my house. It has a buttery shortcrust that holds a custard-rich filling of sweet leeks, fragrant onions, and gooey Gruyere. If you have ever been put off by dry tarts, this one will convert you. The trick is a generous pour of cream and a low, slow bake that keeps everything luxuriously soft. I love serving this tart for brunches or lazy weekend lunches.

I first made this tart as a way to use up extra leeks from my garden, and it ended up becoming a family tradition for Sunday lunch. The scent of onions and butter baking in the oven still makes everyone wander into the kitchen asking when it will be ready.

Ingredients

• All purpose flour: Lends structure and tenderness to the crust, and I always sift it for the lightest result. Choose a high quality unbleached flour for best flavor.
• Unsalted butter: Ultra cold is essential for a flaky shortcrust. European style butters are creamier and result in a richer crust.
• Chilled water: Brings the dough together but do not overdo it. Only add enough for the dough to just come together.
• Leeks: Look for firm, bright stalks with as little yellowing as possible. Wash thoroughly to remove any hidden grit.
• Yellow onion: One small one brings subtle sweetness. A fresh onion with papery, taut skin will be less pungent.
• Unsalted butter or olive oil: Gives richness and helps to caramelize the vegetables for deep flavor.
• Garlic: Minced fresh garlic smells incredible but jarred can work in a pinch.
• Eggs: Large eggs bind the filling and make it lush. Room temperature eggs mix in most smoothly.
• Thick cream: Go for a rich heavy cream, not half and half. It is the difference between a silky filling and a dry one.
• Regular salt: A fine salt seasons both crust and filling evenly.
• Black pepper: Makes the tart aromatic. Freshly cracked has the most flavor.
• Ground cumin: Optional but wonderful for a warm, earthy note. Seek a spice jar with a strong aroma when opened.
• Gruyere cheese: Shredded. Pick a young Gruyere for a gooier melt and nutty flavor. Shred it yourself for best melting.

Step-by-Step Instructions

Prepare the Shortcrust Pastry:

Add the flour and salt to the bowl of your food processor and pulse to combine. Scatter in the cold butter cubes and pulse until the mixture looks like coarse crumbs with some pea sized bits. Drizzle in the chilled water a tablespoon at a time pulsing between each addition. Stop when the dough just begins to clump into a ball.

Roll and Chill the Dough:

Take the dough out and place it onto a lightly floured sheet of baking paper. Shape it gently into a disk with your hands to avoid overworking. Lay another sheet of baking paper on top and use your rolling pin to roll it into a large rectangle or round about one half centimeter thick. Chill the dough in the fridge for an hour to let it rest which helps it roll out without shrinking later.

Line and Prepare the Baking Pan:

Gently peel the chilled dough off the baking paper and set it into your tart pan pressing it evenly up the sides. Use a fork to poke small holes all over the bottom to let steam escape and avoid soggy crust. Pop the lined pan back in the fridge for half an hour and for the last fifteen minutes pop it into the freezer so it goes into the oven very cold for maximum flake.

Blind Bake the Pastry:

Set your oven to one hundred eighty degrees Celsius. Cover the chilled pastry crust with parchment and fill with pie weights or dried beans. Bake for ten to fifteen minutes until the edges are barely golden. Take out the weights and let the shell cool while you handle the filling.

Cook the Leek and Onion Filling:

Cut the leeks in half lengthwise then rinse well under running water to dislodge any dirt. Slice the white and light green parts thinly. Peel and slice your onion just as thin. Melt the butter in a large non stick skillet over medium heat. Add the leeks onion and garlic. Stir them gently for five to eight minutes until the onions go translucent and the leeks soften fully. The veg should not brown. Take off the heat and allow to cool a bit.

Prepare and Bake the Tart:

In a mixing bowl whisk together the eggs thick cream salt pepper and cumin if using until smooth and pale. Stir in the cooled leek and onion mixture along with the shredded Gruyere. Pour this filling into your pre baked tart shell and gently shake to level it. Slide the pan into the oven and bake for twenty five to thirty five minutes until the center is set and the top barely tinged gold. Let it cool for at least ten minutes before you cut and serve for clean slices.

My favorite part of making this tart is that moment when the Gruyere starts to melt into the creamy filling. The kitchen fills with a nutty buttery aroma that makes every family member hover nearby. The leeks go from assertive to meltingly tender which is why this is now my go-to way to cook them.

Storage Tips

Let the tart cool fully before storing. Wrap leftovers tightly and keep in the refrigerator for up to four days. For longer storage slice and freeze individual pieces between wax paper then reheat gently in a low oven. I have found the crust stays crisp if reheated instead of microwaved.

Ingredient Substitutions

If Gruyere is hard to find swap in Emmental or a good Swiss. Even sharp white cheddar gives a crowd pleasing edge. Swap the cream for full fat crème fraiche for a gently tangy finish or use half and half for a slightly lighter result. Substitute spring onions or even shallots for leeks if needed though the flavor will be milder.

Serving Suggestions

Cut the tart into slender slices for appetizers or larger wedges for a main meal. Pair it with a simple green salad dressed with lemon and olive oil or a bowl of tomato soup. It shines at brunch alongside roasted asparagus or as part of a picnic spread. I often tuck a slice into lunch boxes for next day enjoyment.

Cultural Backstory

Leek and cheese tarts are a staple of French countryside kitchens where cooks make use of whatever is fresh and abundant. Gruyere hails from Switzerland but its nutty character is beloved in northern French baking. This combo is classic for a reason. It is comfort food with rustic roots.

Give this tart a try and you will taste why it is so beloved in my family. Happy baking and bon appétit!

Recipe Q&A

→ How do I prevent the tart base from getting soggy?

Blind baking the pastry before adding the filling creates a barrier, keeping the base crisp even after baking with the creamy filling.

→ Can I substitute the butter with olive oil for the filling?

Yes, olive oil can be used instead of butter for sautéing leeks and onions, adding a subtle, fruity note.

→ Which pan shape works best for this tart?

Both a rectangular (14x4.5 inch) or a round (9.5 inch) tart pan create beautiful results with a uniform bake.

→ How do you know when the tart is fully baked?

The filling should be set and just golden on top, while the pastry edges appear deeply golden and crisp.

→ Is it possible to prepare the tart ahead of time?

The pastry base and sautéed filling can be prepared in advance; assemble and bake fresh for best texture.