In a heavy bottom saucepan heat the butter and sugar over medium/low heat with occasional stirring.
Once the butter is melted and the sugar is fully dissolved, increase the heat to medium. It’s ok to stir occasionally to help distribute the heat.
Once the mixture comes to a gentle boil, place a candy thermometer in the pot and let the mixture gently boil away. You want to stir the candy mixture as little as possible at this point. If it’s boiling gently it will be fine…resist the temptation.
Keep an eye on the thermometer. You want to bring the butter sugar mixture to the “hard crack stage” (about 10-12 minutes) which is 310F. This temperature assumes you are at sea level. See Notes for details on how to adjust for different altitudes.
Once at 310F remove the pan from the heat. Be careful the mixture is very hot!!! Stir in the sliced almonds and allow it cool off the heat for a couple of minutes.
Pour into silicone molds. Again, be careful not to touch the toffee as it is VERY hot!. Use a rubber spatula to help push the toffee into the molds as cleanly as possible. Then set the molds aside to cool.
Once the toffee has cooled for about 20 minutes, it should be firm but still soft enough to cut without shattering. Remove the toffee from the molds and cut into small 1 inch to 1.5 inch logs. If the toffee has lots of excess butter you can use a paper towel to dab the excess. See Notes about cutting and lengths.
Place the logs on parchment paper and allow them to fully cool, about 30 more minutes.
Once toffee is fully cool, cut up your chocolate into small chunks, and place in a microwave safe bowl or cup along with the shortening. I like to use a 2 cup pyrex measuring cup.
Place in the microwave for 30 seconds. Give the chocolate a good stir, even though it probably doesn’t look like anything melted. Heat in microwave for another 30 second burst and stir again. Finally another 20 second burst followed by a good stir. If more heat is needed give it 10 second bursts with stirring after until you have a fluid chocolate mixture.
Place one toffee piece into the chocolate and completely enrobe it. Remove with a fork and shake off excess chocolate. Place the chocolate covered toffee into a bowl with the finely chopped almonds. Completely cover with the almonds by rolling it around and then place it onto a parchment paper-lined baking pan to completely set. Repeat with the rest of the toffees.
Place the baking pan in the fridge to help the chocolate set for about 20 minutes.
Almond Roca can be stored in the fridge or on the counter, but it is normally served at room temperature. Enjoy!