Begin by melting the white chocolate in a bowl set over simmering water. In a saucepan, heat the whole milk and vanilla until just warm. Gradually add this to a mixture of egg yolks, caster sugar, and cornflour. Stir continuously until it thickens, returning it to low heat if needed. Mix in the melted chocolate and refrigerate until set.

Slice the rhubarb into small pieces and place them in a pan. Add the sugar, crushed cardamom, and a splash of fresh orange juice. Cook over medium heat, stirring gently until the rhubarb softens but remains intact, about 5–7 minutes. Allow it to cool completely.

In a mixing bowl, combine the plain flour, light brown sugar, and ground ginger. Stir in the chopped stem ginger and melted butter until crumbly. Spread the mixture onto a baking tray and bake at 350°F for 15–20 minutes or until golden brown. Let it cool completely, allowing it to become crunchy.

In your serving dishes, add a layer of the cooled rhubarb compote, followed by the chilled custard. Finish with a generous sprinkle of ginger crumble on top. Serve immediately or refrigerate until serving.