Method

Make the Base

Preheat the oven to 200°C/180°C fan/gas 6. Line a 20 x 20cm square tin with baking parchment, leaving an overhang for easy removal.
Beat together the butter and sugar until fluffy. Sift in the plain flour and cornflour, then stir to form a soft dough. Press evenly into the tin, prick all over with a fork, and bake for 15–20 minutes until pale golden. Cool completely in the tin.

Prepare the Custard

In a pan, gently heat the cream and vanilla until steaming. Meanwhile, in a heatproof bowl, whisk together the egg yolks, sugar, cornflour, and plain flour into a smooth paste. Slowly add the warm cream to the egg mixture, whisking constantly.

Thicken & Set

Soak the gelatine in cold water for 5 minutes. Return the custard mixture to the pan and cook over medium-low heat, whisking, until thickened and bubbling (about 4–5 minutes). Remove from heat.
Squeeze the water from the gelatine and stir it into the hot custard until dissolved. Pour over the cooled shortbread base, level the surface, and chill for at least 3 hours until fully set.

Finish with Strawberries

Arrange the sliced strawberries in neat, overlapping rows over the set custard. For a glossy finish, brush lightly with warmed, sieved jam.

Serve

Cut into 9 large or 12 smaller squares. Best served the day it’s made, though it will keep chilled for up to 2 days.