Grease or oil a large rimmed baking sheet. Set aside.

In a deep pot over low heat, combine the butter and sugar and cook, stirring constantly with a heatproof spatula or wooden spoon until the butter is completely melted and the sugar is dissolved. (Don’t rush this step! It may take up to five or six minutes for the sugar to dissolve but you don’t want the heat too high during this part of the process.)

Once the sugar is dissolved and butter melted, turn the heat up to medium and stir gently as the mixture comes to a boil. Again, this may take a few minutes. Once it comes to a boil, clip a candy thermometer to the side of the pan and continue stirring gently as it cooks.

During this time you want to stir the mixture gently back and forth (like a figure eight).

The mixture will gradually get darker until it reaches 300 degrees F (in the hard crack stage).

Once the mixture hits 300 degrees F, Immediately take it off the stove and stir in the finely chopped almonds.

Pour the candy onto the prepared baking sheet, taking care not to scrape the bottom of the pot as you pour it out.

Quickly spread the toffee into an even layer on the baking sheet using your spatula (or an offset spatula) – it will cool quickly which then makes it hard to spread.

Sprinkle the chocolate chips over the hot toffee, tent with tinfoil (if needed), and let it melt for 3-4 minutes. (We've gone tented and no-tented with no significant difference. It may depend on the content of cocoa in your specific chocolate though. If it's not melting all the way, tent.)

Spread chocolate evenly and top with extra chopped almonds if desired.

Allow to cool completely. This may take a few hours. (You can refrigerate it to let the chocolate set up but sometimes the quick cooling from the refrigerator can cause the chocolate to bloom. Bloom is white streaks and blotches that develop in the chocolate while it cools. It does not affect the taste but it lacks that smooth, shiny chocolate finish.)

Once cool and the chocolate is set, break into pieces.