1 c. butter (2 sticks)
1 c. white sugar
1 T. water
chocolate chips, or chocolate candy bars
Line a cookie sheet with foil or parchment paper. Set aside. Put butter, sugar and water in a saucepan. Stir over LOW heat until butter is completely melted and sugar is completely dissolved. Slowly turn the heat up to medium-low/medium. Continue stirring as it slowly comes to a boil (if it's not coming to a boil at medium-low, slowly turn it up to medium).
Insert a candy thermometer into the pan (clip it onto the side if you have a cool clippy thing). Keep stirring as it boils and thickens until it reaches about 300 degrees (the Hard Crack stage). Shortly before this it will change color from off-white to about the color of peanut butter. The texture will also start to change, so don't be alarmed.
When it reaches the right temperature/stage, quickly pour onto prepared cookie sheet and spread out to desired thickness with a spatula. I just spread mine into a large oval. It cools quickly, so move fast! After about 10 seconds, sprinkle chocolate chips or chocolate bars over the toffee. Wait a minute or two for them to start to melt, and then spread all over the toffee with a knife or spatula. Sprinkle chopped almonds all over. Let cool completely and then break into shards.
Extra tips: If the butter separates at the end, it means you brought it up to a boil too fast (trust me, I know from experience). Make sure the butter is all the way melted and the sugar is dissolved before you turn up the heat. Also, I know some people like chocolate and nuts on both sides of the toffee. Just wait until it cools and then flip it over, spread some already-warmed chocolate over the backside and sprinkle with additional nuts. You can also add chopped almonds to the toffee right before spreading it out on the cookie sheet. This would be more like almond roca. I've never tried it, but it sounds good!