Wash the leek thoroughly, trim off the dry root end, cut the top in half lengthwise, then chop coarsely. Heat olive oil in a skillet over medium-high heat. Spread the chopped leek evenly across the pan. Let it cook without stirring until the underside develops a deep golden color, then stir-fry. Once the leeks have softened, remove from heat.
Slice the cremini mushrooms thinly and microwave them for 5 minutes in a container. Strain to remove excess moisture.
In a mixing bowl, combine the drained mushrooms and sautéed leeks. Add parmesan cheese, salt, and black pepper, and mix well. Set aside and let it cool to room temperature before using.
Cut the unsalted butter into small cubes and freeze for at least 1 hour.
In a mixing bowl, combine the flour, sugar, and salt. Stir well. Add the frozen butter cubes and coat them thoroughly with flour.
Use your fingers to flatten the butter into thin flakes. Add the ice water a little at a time, stirring lightly after each addition to distribute moisture evenly. Stop when there’s no loose flour left at the bottom of the bowl. The dough will look crumbly at this stage.
Transfer the dough onto a work surface and gently press it together into a ball without kneading. Flatten into a disk, wrap in plastic wrap, and freeze for 20 minutes.
Preheat the oven to 200°C (400°F).
After 20 minutes, take out the dough. Dust the work surface and dough lightly with flour to prevent sticking. Roll it into a roughly 26 cm diameter circle, about 4 mm thick. Rotate the dough frequently and dust with more flour as needed to prevent sticking. Trim the edges to form a neater circle.
Line a baking sheet with parchment paper and transfer the dough onto it. Brush a thin layer of extra olive oil over the surface.
Spread half the filling over the center of the dough, leaving a 3–4 cm border. Crumble the ricotta cheese and scatter it over the filling. Then layer on the remaining filling and smooth it out gently.
Fold the edges of the dough over the filling, forming a rustic pleated shape. Gently pinch the folds to seal. Brush the crust with egg wash (extra).
Bake in the preheated oven for about 30 minutes. Let cool for 10 minutes before slicing and serving.
Heating the leeks and mushrooms removes most of their water content, preventing the filling from releasing too much moisture during baking and softening the crust.
Other types of mushrooms, like shiitake, can also be used. For richer flavor, you can sauté the mushrooms in butter instead of microwaving—though microwaving is quicker and easier.
Adjust the amount of salt and black pepper to taste. You can substitute ricotta with brie, goat cheese, or blue cheese. Adjust the seasoning in the leek-mushroom filling based on the cheese’s saltiness.
Always let the filling cool to room temperature before assembling. Hot filling will cause the butter in the dough to melt prematurely, resulting in a less flaky crust.
Keeping the butter from melting too much during preparation is crucial for a flaky crust. Melted butter releases water into the dough, increasing gluten formation and preventing the development of distinct flaky layers. Coating the butter with flour and using ice water helps slow down melting.
You can also use a food processor to make the dough, pulse the flour, sugar, salt, and butter together until the butter forms coarse uneven crumbs before adding the ice water.
You can use a silicone baking mat instead of parchment paper for easier removal and transfer. Since silicone mats conduct heat more slowly, you may need to adjust the baking time accordingly.
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