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Caramelized Leek Tart

by practicewithdanielle
top down shot of leeks on a caramelized leek tart

One reason I’m excited about French month is that I get to experiment with pastry. It’s one of those things you go into, expecting to fail because it relies on science, temperatures and exact measurements.

I’m more of a let’s-throw-it-together-and-see-how-it-works-out kind of baker.

Lucky for me, my first go at puff pastry came out perfectly.

*Rough puff* to be exact. If you watch Great British Bake Off (why aren’t you watching this yet), you know it’s a staple in their kitchen. It’s puff pastry that takes short cuts and comes together VERY quickly.

My rationale for making rough puff is two-fold:

1. I like to make things myself if it’s within reach rather than buying it
2. It cost $11 at Whole Food and are they serious?


Butter layers are critical to flaky puff pastry.

I used this recipe over at Bon Appetit, followed it to a T, and it came out perfectly. Hop over to their site for step by step directions because I haven’t found the patience for shooting those myself.

Once you’ve got your rough puff, you’ll use either a 14oz package from the store or half the recipe I shared above.

This Caramelized Leek Tart a stellar recipe.

side view of caramelized leek tart cut into pieces on parchment paper

I changed a few things from the Bon Appetit version out of necessity but also I wanted even MORE caramelization (a sweeter vinegar, more sugar).

This one uses leeks because they are in season and I’m obsessed with leeks. But also fennel? Or carrots? Or onions!

top down shot of leeks on a caramelized leek tart

Really any vegetable that can handle a little sweetness and wants to get flipped upside down over a flaky puff crust.

The dijon mustard adds a critical kick of flavor, and the parmesan layer helps bind everything together without making this “cheesy”.

side view of caramelized leek tart

To make this a meal – serve with a salad or piece of protein. Or if you’re like me and like a little sweet/savory action for breakfast, serve with a side of scrambled eggs.

I’m going to make this again and again this month so keep an eye out for different versions.

top down view of caramelized leek tart on parchment paper

I adapted this recipe, found on Bon Appetit.

Caramelized Leek Tart

(Start making 75 minutes before you want a Caramelized Leek Tart)

1 14oz package frozen puff pastry, thawed*
Flour for dusting
6 leeks, roots, and dark green ends removed, sliced in half lengthwise
2 Tbsp olive oil
pinch of salt and pepper
1/4 cup red wine vinegar
2 Tbsp unsalted butter
1 Tbsp sugar
1 tsp fresh thyme leaves
2 Tbs Dijon mustard
1/2 cup Parmesan, finely grated
Coarse sea salt and more thyme to finish

*This recipe is much faster when you buy store-bought puff pastry. OR you could make your own rough puff like I did. I used this recipe on Bon Appetit and needed half for this Caramelized Leek Tart.


A note on cast iron – just buy a cast iron pan. They are great at retaining an even heat and stand up to high temps in the oven. They are also very inexpensive and will last forever. You could try this with a steel pan but do not use non-stick as it will not hold up in the oven. 

Preheat your oven to 400F.

Roll out your puff pastry on a lightly floured surface and measure a 10inch circle (or whatever size cast iron pan you’re using). Cut the puff pastry to fit the pan. Prick a fork all over the puff pastry and gently cover and store in the fridge until ready to use.

Cut leeks so the white and dark green ends are removed. Cut lengthwise. Cover with olive oil, salt, and pepper and arrange cut side down on a baking sheet. Bake for 20 minutes or until lightly browned. Once cooked and cooled slightly, remove the tough outer layer of the leeks and discard.

While your leeks are roasting, heat up the vinegar in your cast iron pan until bubbling. Simmer for 1 minute. Then add sugar, butter, and thyme. Remove from heat and cool slightly.

Lay your leeks cut side down in the vinegar mixture in the cast iron pan. Whatever pattern you lay them down, this will be the top of your tart. Get creative!

Brush the back side of the leeks with dijon mustard and then sprinkle on parmesan cheese. Lay the puff pastry over the whole thing and cut three large slits down the puff. Cut all the way through so steam can release.

Bake for 45 minutes. If your puff is browning too much, you can lightly cover with aluminum foil and keep baking.

Remove from oven, let cool for 5 minutes, then cover with a large plate, AND FLIP QUICKLY. If any leeks get stuck to the pan, just carefully scrape off and place them on your tart.

Sprinkle more thyme and coarse sea salt on top.


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