Line an 11x7 inch baking dish with foil, or prepare a silicone brownie bite pan (with 24 cavities). Arrange the whole almonds in a single layer on the prepared surface.

In a heavy-bottomed saucepan, combine the butter, margarine, granulated sugar, kosher salt, and vanilla extract. Cook over medium-high heat, stirring constantly with a wooden spoon, until the butter melts. Bring the mixture to a rolling boil.

Continue boiling and stirring for an additional 5-7 minutes, or until the candy reaches the color of almonds (approximately 300 degrees Fahrenheit on a candy thermometer). Carefully pour the hot toffee mixture over the arranged almonds. If using a brownie bite pan, use a small metal scoop to quickly fill each cavity.

Allow the toffee to cool completely until set, which typically takes about 2 hours.

Once the toffee is completely cooled and firm, spread the melted milk chocolate evenly over the top. Sprinkle generously with the ground walnuts. If desired, after the top chocolate layer has set, you can carefully flip the toffee and repeat the chocolate and walnut coating on the bottom. Once set, remove the toffee from the pan. Store in an airtight container or cut into individual pieces to serve.