Preheat the oven to 200°C and grease a 12-hole petit four tin.
Pulse flour, butter, sugar, and salt in a food processor until the mixture looks like breadcrumbs.
Add egg yolks and cream to form a dough, then chill for 30 minutes.
Dissolve brown sugar and butter in a pan, stir in cream, and cool the toffee mixture.
Roll out dough, cut 12 circles, line the tin, and bake for 12 to 16 minutes until golden.
Cool the pastry cases on a wire rack.
Blend bananas and fold into whipped cream along with icing sugar to create the mousse.
Fill each pastry case with toffee.
Pipe the banana mousse over the toffee.
Finish by scattering shaved chocolate over the pies.