Cut the butter into small pieces and place in the saucepan along with the sugar and the water.
Put the stove on medium heat. Stir with a whisk continually until the mixture reaches 305 degrees on the candy thermometer. It takes between 25-35 minutes usually.
Once the mixture reaches 305 degrees, remove from the heat, add the vanilla extract and stir. Watch out, because it will give off steam.
Then, add the pecan pieces to the mixture and stir.
Pour the toffee into the greased pan and use the spatula to spread it out.
Sprinkle the chocolate chips on top of the toffee and wait a few minutes for them to soften. You may need a little more than a cup depending on your sprinkle technique, so have the bag handy for more. Then, spread them into a smooth layer with the spatula
Sprinkle the pecan dust on top of the chocolate
Put the toffee in the freezer/fridge for at least 30 minutes to cool.
When the chocolate pecan toffee is hard, you can break it into bite-sized pieces and enjoy.