Start by lining a baking sheet with parchment paper. This will prevent the toffee from sticking and make cleanup a breeze.
In a heavy-bottomed saucepan, combine the 2 cups of salted butter and 2 cups of sugar. Stir gently over medium heat until the butter is melted.
Continue to cook the mixture over medium heat, stirring constantly. You want to reach a temperature of 300°F (hard crack stage). Keep an eye on the candy thermometer, as this step is crucial for the perfect texture.
Once you reach the desired temperature, remove the saucepan from the heat. Stir in the 2 teaspoons of vanilla extract and 1 teaspoon of salt. Be cautious, as the mixture may bubble up when you add the vanilla!
Quickly pour the hot toffee mixture onto the prepared baking sheet. Use a spatula to spread it evenly, but work fast as it will begin to set.
While the toffee is still hot, sprinkle the 2 cups of milk chocolate chips generously over the surface. Allow them to sit for a few minutes to melt, then spread the chocolate evenly over the toffee. Finally, sprinkle the 1 cup of chopped pecans on top, pressing them gently into the melted chocolate.
Let the toffee cool completely at room temperature. Once set, break it into pieces and store it in an airtight container.
