Prep: Lightly grease a 9x12 or 9x9-inch metal baking dish and line it with parchment paper, ensuring the top surface of the parchment remains ungreased.

Toast the Nuts: In a skillet over medium heat, warm the whole almonds for 5-7 minutes, stirring every 30 seconds to prevent burning. Alternatively, roast them on a baking sheet in an oven at 325°F for 10-15 minutes. Coarsely chop the almonds, then scatter half of them evenly across the bottom of your prepared baking dish. Reserve the other half for later use as a topping.

Prepare the Toffee: In a large, heavy-bottomed saucepan (3-4 quarts), combine the butter, sugar, vanilla, and salt. Set the saucepan over medium heat, stirring constantly with a wooden spoon until the butter fully melts and the mixture begins to boil. Continue stirring gently until the mixture develops a rich caramel hue and reaches 300-310°F on a candy thermometer, indicating the hard crack stage. This process should take roughly 8-10 minutes; be cautious, as the mixture will be extremely hot and can darken rapidly near the end.

Pour and Spread: Carefully pour the hot toffee mixture into the prepared baking dish, tilting the pan to distribute the mixture evenly over the nuts. It does not need to cover the entire surface or have a perfect appearance.

Add the Chocolate: While the toffee is still hot, sprinkle chocolate chips evenly over the surface. Allow them to sit for about 2 minutes until they begin to soften and glisten. Using an offset spatula, spread the melted chocolate evenly over the toffee layer. Sprinkle the reserved chopped nuts over the top, gently pressing them into the softened chocolate to ensure adherence.

Cool and Set: Let the toffee cool at room temperature for at least 2 hours, or until the chocolate has completely set. Once firm, cut or break the toffee into desired pieces. Store in an airtight container at room temperature for up to a week.