Arrange almonds in a single layer on a foil-lined baking dish or in a brownie bite pan. Set aside.

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

Continue boiling and stirring for 5 to 7 minutes, until the mixture turns a deep golden color (~300°F). Quickly pour over the almonds in the pan.

Let the toffee cool completely, about 2 hours.

Once cooled, spread melted chocolate over the top of the toffee and sprinkle generously with ground walnuts. Allow the chocolate to set before cutting into pieces.