Line a baking dish with foil and arrange almonds in a single layer. Set aside.

Combine butter, margarine, sugar, salt, and vanilla extract in a heavy pan. Cook over medium-high heat, stirring constantly until butter melts and mixture reaches a rolling boil.

Continue boiling and stirring for 5 to 7 minutes until the candy turns the color of almonds or reaches 300 degrees Fahrenheit. Pour the caramel over the almonds and spread evenly.

Allow the toffee to cool completely, about 2 hours.

Spread melted chocolate over the cooled toffee. Sprinkle generously with ground walnuts. Let set before breaking into pieces and serving.