All-allium quiche

Roll the cold pie dough out to about a 13 inch round, letting it sit a minute or two first to soften slightly.

Slide the springform base under the dough, fold the edges in over the base, clip the ring on, then unfold and press the dough up the sides to an even height.

Chill the lined pan in the freezer 10 to 15 minutes until firm and relaxed. Heat the oven to 425F with a rack in the centre.

Peel a yellow onion, halve it through the stem end, oil the cut faces and char them undisturbed in a hot pan on one side only.

Crisscross two sheets of foil into the chilled crust, pressing into the corner between base and side, and fill with dried beans.

Bake at 425F for 20 to 25 minutes, until the top edge of the crust is set, dry and lightly golden.

Slice the stem end off the charred onion halves and separate the layers; reserve the prettiest inner pieces as petals and chop the rest for the filling.

Chop the shallot, leek white and light green, scallion and garlic, keeping all the pieces a similar size so they cook at the same rate.

Crisp the chopped pancetta in the butter over medium heat about five minutes, rendering some but not all of its fat, leaving a little chew.

Lift the pie weights out by gathering the foil into a bundle and return the crust to a 325F oven until the bottom is really dry with some golden browning.

Lift the pancetta out with a spoon, letting the fat drain back into the pan, and set aside.

Add all the chopped alliums to the pancetta fat and cook until soft, translucent, collapsed and browning at the edges.

Season lightly with salt and heavily with black pepper, slide off the heat and stir in the white wine vinegar.

Beat one of the four eggs until there are no streaks.

Mix a couple tablespoons of flour with a dash of water into a very soft dough and smear it into any cracks in the crust.

Brush the beaten egg over the crust, concentrating on the bottom and the corner where the bottom meets the sides, to seal it. Save the rest of the egg for the filling.

Return the crust to the 325F oven about five minutes until the egg is set.

Blend the room temperature half and half with the reserved egg, the three remaining eggs and the kosher salt, keeping the blender submerged so no air is worked in, until smooth.

Scatter the cooked alliums over the bottom of the crust, then the pancetta, then pour the custard in slowly right to the top.

Set the reserved onion petals in so a little custard runs into them and they stick out of the surface.

Bake at 325F for 50 to 60 minutes. It is done when the surface has only a slight jiggle and the edge has puffed a little; hers went about 55 minutes.

Cool completely, several hours, before removing the ring and slicing.