You will need a 25cm diameter tart tin and baking parchment paper. Prepare your tart tin by lining the bottom with a circle of baking parchment.
To make your base, pulse biscuits and crystallised ginger in a food processor until it forms crumbs. Add melted butter and pulse so crumbs are completely covered in butter.
Transfer biscuit crumbs into tart tin. Distribute evenly using your hands, working the mixture up the sides of the tin to create a wall.
Cover base with plastic wrap and place in the freezer for at least 30 minutes to set.
To prepare filling, submerge gelatin in a small dish of cold water. Leave to soak for 5 minutes. Meanwhile, add 3 tablespoons of hot milk into a mixing bowl. Remove gelatin leaves from water, squeeze to get rid of excess water, and stir, one by one, into the milk (they will dissolve instantly). Add yoghurt and maple syrup and whisk together well.
Remove tart case from freezer. Pour filling into case and distribute evenly. Drizzle with the reserved Black Doris plum topping. Refrigerate for at least 1 hour (max 24 hours).
Serve with tinned Black Doris plums.