Line an 11x7 inch baking dish with foil and arrange almonds in a single layer. Set aside.

In a heavy saucepan, combine butter, margarine, sugar, salt, and vanilla. Cook over medium-high heat, stirring constantly until butter melts and mixture begins to boil. Bring to a rolling boil.

Continue boiling and stirring for 5-7 minutes until the candy turns a caramel color, approximately 300°F. Quickly pour over the almonds in the pan.

Allow the toffee to cool completely, about 2 hours.

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