Thaw commercial puff pastry according to the instructions on the package. If using hand-crafted puff pastry, ensure it is chilled.

The vegetables need to be precooked, cooled and blotted dry before the pie is assembled. The bell peppers and zucchini in particular retain a great deal of moisture and must be as dry as possible to prevent the pastry from becoming soggy.

Bell peppers: Place the whole peppers on a parchment- or foil-lined baking tray. Bake in a preheated 375°F (190°C) oven until the peppers have darkened in spots and are starting to collapse, about 45–55 minutes, rotating the pan once during baking. Transfer to a bowl and cover tightly with foil or plastic wrap. When cool enough to handle, remove the skins, cores and stems, keeping the peppers in large pieces. If not using right away, store on a plate between paper towels, cover and refrigerate. Blot completely dry before using.

Zucchini: Slice the squash horizontally into ¼-inch (6 mm) thick ribbons. Place the ribbons on a baking tray lined with foil or parchment paper, without overlapping. Brush with oil and bake in a preheated 375°F (190°C) oven until soft (zucchini will shrink slightly), about 25 minutes, rotating the tray once during baking. If not using right away, store between paper towels, cover and refrigerate. Blot completely dry before using.

Mushrooms: Wipe clean and slice the mushroom caps horizontally, about ¼ inch (6 mm) thick, so as to increase the surface area. Reserve the stems for another use. Heat 3 Tbsp (45 mL) oil in a large skillet over medium heat. Working in batches, adding a pinch of salt to each batch, add the mushrooms in a single layer and cook until the mushrooms have browned, about 5 minutes, turning them over once. Continue to cook until the mushrooms are tender. Cool and blot completely dry before using.

Kale and garlic: Using a slotted spoon within easy reach, heat 3 Tbsp (45 mL) oil in a large skillet over medium-low heat, add the garlic and cook until just starting to brown, about 30 seconds. Remove the garlic with the slotted spoon and reserve. Working in batches, cook the kale in the garlic oil until completely wilted, about 3–4 minutes, turning the greens as necessary to prevent burning. Add a pinch of salt, chili flakes, lemon juice and the cooked garlic and mix to combine. Cool and blot completely dry before using.

Roll the puff pastry onto a flour-dusted work surface (or if it’s sticky, onto a sheet of parchment paper dusted with flour) and into a circle about 1/4 inch (6 mm)

thick. Using a 9 ½-inch (24 cm) fluted tart pan, if you have one, cut the pastry to form a fluted edge. Alternatively, use a 9 ½ inch (24 cm) plate or a saucepan lid as a template to cut a circle. (The pastry will be re-rolled later to ⅛ inch/3 mm to create a slighter larger top to accommodate the filling.) Wrap in plastic, label “top” and refrigerate.

Gather and re-roll the remaining pastry into another circle 9 ½ inches (24 cm) in diameter and ⅛ inch (3 mm) thick, as directed above. Wrap in plastic, label “base” and refrigerate.

Ensure all your vegetables have been blotted completely dry before you start layering the ingredients, otherwise your pastry can become soggy. You’ll want to assemble the pithivier on a parchment-lined baking tray (or any flat kitchen tray) that can easily fit in your fridge, as the pastry is chilled before baking. It’s easier to maneuver the pastry with a tray underneath it.

Remove the pastry “base” from the fridge. Sprinkle with half of both the Parmesan and the Gruyère, leaving a 1-inch (2.5 cm) border. Neatly layer the ingredients, maintaining a 1-inch (2.5 cm) border throughout. Don’t worry about the exact order of ingredients, the idea is to have neat layers. And don’t forget to add a small but well-distributed pinch (a mere ⅛ - ¼ tsp) of kosher salt to each layer of vegetables. (If using table salt you’ll need even less, as the crystals are more compact and lend a saltier punch.)

As a guide, spread half the kale over the cheese with a grind of pepper, then add half the ham spread with half the mustard. Add a layer of roasted pepper, then the mushrooms, and spread with the roasted tomato pesto to form an even layer. Layer with the remaining cheeses and ham and spread with the remaining mustard.

Top with the remaining kale and a grind of pepper. Follow with the zucchini and

a pinch of salt. You should have a neat, well-seasoned stack of ingredients with a clean 1-inch (2.5 cm) pastry border.

Mix together the egg yolk and whipping cream and brush the border with the mixture.

Remove the pastry “top” from the fridge. Roll the pastry lightly to create a slightly larger circle (about ¼ inch/3 mm) thick, being mindful to retain the fluted edge (if you have one).

Place the pastry neatly over the stack of ingredients, smoothing the pastry with your hands to form a neat mound with a flat 1-inch (2.5 cm) border. Wrap in plastic and refrigerate (with the parchment and tray beneath) or freeze for at least 20 minutes to firm the pastry.

Preheat a parchment- or foil-lined baking tray in a 425°F (220°C) oven.

Brush the pastry with the yolk/cream mixture, being mindful to cover the entire pastry. Score the (firmed) pastry with a sharp knife, starting from the centre and moving toward the edges in ¼-inch (6 mm) increments.

Transfer the pithivier, and the parchment beneath it, to the preheated baking tray using a pizza peel or flat-edged baking tray. Alternatively, carefully remove the baking tray from the oven and transfer the pastry, with the parchment underneath it, onto the heated tray.

Bake for 20 minutes, rotating the pan once during baking. Cover loosely with foil, reduce the temperature to 375°F (190°C) and continue to bake until the pastry is completely cooked through, about 15–20 minutes more.

Cool on a wire rack, removing the parchment beneath the pastry. Cool for at least 45 minutes before slicing. Best served slightly warm or at room temperature.