Preheat the oven to 350. Line a 8 by 8 baking dish with foil with sides extending over the edge for easy removal of bars. Spray foil woth non stick spray
Make Shortbread Crust
In a bowl beat butter, sugar and vanilla until light and fluffy
Add flour and salt and beat just until the dough forms clumps
Press onto prepared pan evenly and bake about 25 to 30 minutes until light golden
Cool completely on a wire rack
Make Caramel Layer
Pour sweetened condensed milk in to a heatproof bowl and stir in salt and vanilla
Place bowl over simmering water, cover with foil and cook until a golden caramel forms about 60 to 90 minutes. Stir occasionally and check to be sure the water level is ok.
Remove from heat and beat until smooth with a whisk.
Spread caramel over cooled shortbread crust. Let caramel firm up about 60 minutes before adding chocolate layer
Make Chocolate Layer
Combine both chopped chocolates and butter in a microwave safe bowl, microwave carefully until just melted then stir smooth
Let sit about 5 minutes to cool a bit then pour over caramel layer
While chocolate is still warm evenly top with Toffee bits
Let chocolate set before cutting g into bars. Refrigerate for easy cutting. To cut remove entire shortbread from pan in one piece, then cut. Store in refrigerator or freeze individual bars for layer
