On a foil-lined baking dish (11x7 inches) or in a silicone brownie bite pan (with 24 bites), arrange almonds in a single layer. Set aside.
In a heavy-bottomed pan, combine butter, margarine, sugar, salt, and vanilla extract. Cook over medium-high heat with a wooden spoon until butter melts, stirring constantly. Bring the mixture to a rolling boil.
Continue boiling and stirring for an additional 5-7 minutes until the candy turns the color of almonds (about 300 degrees Fahrenheit). Pour over the prepared almonds. If using a brownie bite pan, use a small metal scoop to quickly distribute the toffee into each bite.
Cool completely. This may take about 2 hours at room temperature.
When the candy is cooled and set, spread the melted chocolate over the top of the toffee. Sprinkle generously with ground walnuts. If you plan to coat both sides, use only half of the chocolate and walnuts. Allow the top to set before flipping and coating the bottom. Once set, pop out of the silicone pan or cut into pieces. Enjoy!
Notes
For best results, use a heavy-bottomed saucepan and stir constantly to prevent butter separation. Ensure the toffee is fully cooled and set before adding the chocolate topping.