Start by greasing a 9x13-inch baking pan with butter or lining it with parchment paper for easy removal later.
In a medium saucepan over medium heat, combine the 1 cup of salted butter, 1 cup of granulated white sugar, 1 tablespoon of light corn syrup, and 3 tablespoons of water. Stir the mixture until the butter is melted and the sugar is dissolved.
Bring the mixture to a boil, stirring constantly. Allow it to boil without stirring for about 4-5 minutes, or until it reaches a deep golden color. Be cautious not to overcook it, as it can burn quickly.
Once the toffee is ready, remove it from the heat and stir in 1 cup of finely chopped almonds or pecans until well combined. Quickly pour the mixture into the prepared baking pan, spreading it evenly with a spatula.
Allow the toffee base to cool completely at room temperature. This step is crucial, as it needs to harden before adding the chocolate layer.
While the toffee cools, melt the 6 ounces of milk chocolate chips using a double boiler or microwave. If using a microwave, heat in 30-second intervals, stirring in between until smooth.
Once the toffee has cooled and set, pour the melted chocolate over the top. Use a spatula to spread it evenly, ensuring every inch is covered.
Let the chocolate layer set at room temperature or refrigerate for quicker results. Once hardened, you can cut the bars into squares or rectangles for serving.
