Preheat the oven to 160°C and grease a 20cm x 23cm baking tin with butter.
Sift flour, cornflour, and sugar into a bowl and stir in almonds, butter, and vanilla seeds.
Press the mixture into the tin and bake for 35-40 minutes until lightly golden, then cool.
Heat sugar and water in a pan until dissolved, then simmer until dark amber.
Stir in cream, butter, and salt, then pour the caramel over the shortbread and cool.
Melt chocolate and butter in a heatproof bowl over simmering water.
Pour chocolate over the caramel, smooth out, and chill for 30 minutes before cutting into 16 squares.