Prepare your pastry base. If using a pre-made shortcrust shell, set it on a serving plate. If making a biscuit base, crush 200g digestive biscuits into fine crumbs (you'll hear the bag rustle as the crumbs get finer), mix with 80g melted unsalted butter, press firmly into a 23cm pie dish, and chill for 20 minutes until the mixture feels set and cool to the touch.

Mash half the strawberries. In a medium saucepan, add 400g of the hulled strawberries. Using a potato masher or the back of a fork, crush them until you have a chunky, juicy pulp — you should see a deep red liquid pooling around the pieces.

Cook the strawberry base. Place the saucepan over medium heat. Stir in the caster sugar, lemon juice, vanilla extract, and salt. Bring the mixture to a gentle simmer — you'll see small bubbles breaking the surface and the kitchen will smell intensely of cooked strawberries. Let it bubble for 3 minutes, stirring occasionally, until the colour deepens to a rich ruby red.

Thicken the filling. In a small bowl, whisk the cornflour with the cold water until the mixture is smooth and white, with no lumps. Pour this slurry into the simmering strawberry mixture while stirring constantly. Within 30 seconds, you'll notice the texture change from watery to glossy and thick — it should coat the back of a spoon like a loose jam. Remove from the heat and let it cool for 5 minutes; the mixture will look slightly translucent and feel heavy on the spoon.

Fold in the fresh strawberries. Gently stir the remaining 400g of fresh strawberry halves into the warm cooked mixture. You want the fresh berries to stay chunky — the contrast between the soft cooked base and the firm raw pieces is wonderful. The mixture should look bright and jewel-like, with whole berries suspended in the thick red sauce.

Fill the pie shell and chill. Pour the strawberry filling into your prepared pastry shell, spreading it evenly with a spatula. The filling should come almost to the rim. Place the pie in the fridge, uncovered, for at least 2 hours — the surface will feel firm and slightly tacky when it's fully set. For a cleaner slice, leave it overnight.

Whip the cream just before serving. In a chilled bowl, pour the double cream, icing sugar, and vanilla bean paste if using. Whisk with an electric mixer on medium speed until soft peaks form — when you lift the beaters, the cream should hold a gentle peak that flops over slightly. You'll hear the sound change from splashing to a soft, thick thud as it thickens. Spread or pipe the cream over the chilled pie just before serving.