A buttery shortbread crust cradles a silky white chocolate custard, crowned with fresh strawberries, blueberries, and raspberries for a bright, glossy finish. Rich, creamy, and delicately sweet, it’s balanced by the tart freshness of peak-season berries.
Preheat the oven to 350°F (175°C). In a medium bowl, whisk together the crust flour, cornstarch, powdered sugar, and a pinch of salt.
Add the softened butter and 1 egg yolk to the dry ingredients and work with your hands until a smooth dough forms.
Press about half the dough evenly into the bottom of a 9-inch tart pan; use the remaining dough to line the sides uniformly.
Bake the crust for 15 minutes. Cool completely on a wire rack. If the crust puffs, gently press it down with the bottom of a flat glass.
For the custard, whisk together the sugar, cornstarch, and a pinch of salt in a medium saucepan.
Gradually whisk in the milk and 5 egg yolks until fully combined.
Cook over medium heat, stirring constantly, until it reaches a gentle boil and thickens; continue simmering and stirring for 2 minutes to fully activate the cornstarch.
Strain the custard through a fine-mesh sieve into a heatproof bowl. Immediately stir in the white chocolate chips, butter, and vanilla until smooth and melted.
Pour the custard into the cooled tart shell. Refrigerate until fully set, at least 6 hours or overnight.
Before serving, top with sliced strawberries, blueberries, and raspberries. If desired, thin strawberry jam with water and lightly brush over the berries for a glossy finish. Serve immediately.