Preheat oven to 350°F (175°C).
Crush cookies into fine crumbs using a food processor.
Mix with melted butter until evenly combined.
Press firmly into a 9-inch pie dish.
Bake for 8–10 minutes. Let cool completely.
In a large heatproof bowl, whisk together eggs, sugar, milk, and cream until smooth.
Place the bowl over a saucepan of gently simmering water (double boiler).
Whisk constantly and heat the mixture until it reaches 167°F (75°C) — thick enough to coat the back of a spoon.
Immediately pour the hot custard over the 400g chopped chocolate in a separate bowl.
Let sit for 1–2 minutes, then whisk until smooth and glossy.
Stir in vanilla and salt.
Pour into the cooled crust. Cover the surface with plastic wrap and chill until fully set, at least 4 hours or overnight.
Whip cream, sugar, and vanilla until soft peaks form.
Spread or pipe over the set chocolate filling.
Drizzle with caramel and sprinkle with flaky sea salt just before serving.
