Have ready a 20cm loose-bottom cake tin at least 5cm deep. In a food processor, whiz the shortbread biscuits to crumbs, add the melted butter and whiz to combine. Press the crumb mixture into the base of the cake tin using the back of a spoon. Chill in fridge.
To make the cheesecake: cut the gelatine leaves into broad strips. Place these in a small bowl, cover with cold water and soak for 5 minutes, then drain. Pour over 3 tablespoons of boiling water and stir to dissolve.
Gently heat the cream cheese, cream, 200g sugar, mango and lemon juice in a medium-size pan, stirring until the cream cheese liquefies, then whisk until smooth. The mixture should be warm but not boiling. Stir in the gelatine solution. Carefully pour the mixture over the shortbread base. Cover and place in the fridge for several hours until set.
To make the passionfruit glaze: scoop out the passionfruit into a small bowl. Soak, drain and dissolve the gelatine as for the cheesecake. Add the 15g sugar and stir to dissolve. Stir the passionfruit pulp a tablespoon at a time into the gelatine solution. You should have about 150ml of mixture: if not, make up the quantity with a little water. Pour the glaze over the top of the cheesecake, then cover and chill for another few hours or overnight.
Run a knife around the edge of the cheesecake and remove it from the tin.
Decorate with the strawberries. Dust with icing sugar to serve.