FOR THE BISCUIT BASE
300g chocolate oaty biscuits, such as Chocolate Wheaten
FOR THE TOFFEE FILLING
115g soft dark brown sugar
397g can sweetened condensed milk
FOR THE TOPPING
450ml double cream
5 ripe but firm medium bananas
1 tsp lemon juice
25g plain dark chocolate, coarsely grated, or chocolate curls
To make the base, melt the butter in a small pan. Break the biscuits into chunky pieces and blitz them to crumbs in a food processor. With the motor running, add the melted butter and blend until thoroughly mixed. Alternatively, put the biscuits in a strong plastic food bag and bash with a rolling pin. Tip the crumbs into a bowl and stir in the melted butter.
Tip the mixture into the centre of a 23cm round x 4cm deep loose-based tart tin and press it firmly into the base and up the sides. Make sure the mix is evenly distributed, especially where the base meets the sides. Chill for 30 mins until set.
To make the filling, melt the butter in a non-stick pan and stir in the sugar. Cook over a low heat, stirring constantly, until the sugar has dissolved and the butter and sugar look smooth with no oil floating to the surface. Add the condensed milk and bring to a gentle simmer, stirring constantly. Cook for 3 mins, stirring, until the mixture turns a deep, creamy caramel brown. Pour the toffee gently onto the biscuit base and quickly smooth over the surface. Leave to chill for at least 1 hr (up to 8 hrs) before topping.
Remove from the tin (this is easier if left at room temperature briefly). Just before serving, lightly whip the cream. It should stand in very soft peaks – any thicker and it will look over-whipped when mixed with the bananas. Diagonally slice 4 bananas and scatter half over the toffee. Fold the rest lightly into the cream and spoon gently on top. Slice the remaining banana and put it in a bowl with the lemon juice. Toss very gently – this will stop the banana turning brown. Decorate the top with the lemony banana slices, poking them into the cream randomly, then sprinkle on the grated chocolate or decorate with chocolate curls. Serve in fairly thin slices, as it is very rich.