Blueberry slab pie

Toss the frozen blueberries and raspberries with the cornstarch, lemon verbena sugar, salt, cinnamon, ginger and cardamom.

Add the lemon juice (no zest here, since the lemon verbena sugar already brings bright flavour) and the vanilla; stir until evenly mixed and coated.

Return the filling to the freezer to stay somewhat frozen, so it does not release too much juice while the pie is assembled.

Beat the chilled dough gently with the rolling pin to make it pliable, then roll it a few inches larger than the slab in both directions, about 16 by 12.

Roll the dough onto the pin, unroll it over the slab from one side and let it slump into the bottom and up the sides without stretching; refrigerate.

Roll the second portion between a quarter and an eighth of an inch thick, about 12 by 16 inches, and cut strips in one direction using a ruler and a wheel cutter.

Beat the egg until there are no streaks, removing any big pieces of white.

Scrape the filling into the bottom crust and press it into an even layer into the corners.

Brush egg wash around the border where the crust meets the edge of the slab.

Drape the strips across the filling in one direction, staggered and overlapping in places with gaps in others; trim the strip ends so they barely pass the rim.

Trim the bottom overhang to about half an inch, egg wash the border, fold the overhang up over itself pressing the strips to seal, and crimp with thumb and forefinger.

Egg wash the top without pooling and sprinkle generously with demerara sugar.

Freeze about 10 minutes until the edge is firm and cold.

Set the slab on a half sheet tray and bake at 425F about 20 minutes.

Turn the oven down to 350F and bake the rest of the way, around an hour total, covering the corners with foil if they brown too fast, until the juices are thick and bubbling slowly.

Cool completely so the filling sets, then slice with a bread knife.