Line a 20cm x 30 cm (8" x 12") lamington/brownie pan with baking paper.
In a medium size pot/saucepan, with a heavy base, place butter and brown sugar.
Place pot/saucepan on stove over medium heat. Stir until butter melts and sugar is well combined. Attach candy thermometer to the side of the pot/saucepan in order to keep an eye on the temperature. Ensure the bulb/end of the thermometer is in the bubbling sugar mixture.
Bring mixture to a medium boil and continue cooking for 8 -10 minutes. Stir the mixture regularly to stop it catching and burning.
Remove mixture from heat when it reaches 145°C/300°F. If not using a candy thermometer please see notes.
Reserve ⅓ cup of the toasted flaked almonds. Add remaining almonds to the toffee mixture and mix well.
Pour mixture into the prepared lamington/brownie pan. Be careful the toffee mixture is extremely hot. Allow the almond toffee to cool on the kitchen bench while you melt the dark chocolate.
In a glass bowl place roughly chopped chocolate. Melt chocolate in the microwave. First for 1 minute, then give the mixture a stir. Then in 30 second bursts mixing well in between. Remove chocolate from microwave when there are a few lumps left and stir until they melt.
Pour chocolate over almond toffee and level it out with a spatula.
Sprinkle evenly with the sea salt. Don't be too heavy handed!
Gently crush the remaining toasted almonds with your hand. don't over do it, just a gentle smush is needed. Then sprinkle almonds over the chocolate.
Place Almond Roca in the fridge for a couple of hours or until set. Using a heavy sharp knife cut into desired size pieces.
Store in an airtight container in the fridge.
Testing the toffee without a thermometerIf you don't have a thermometer grab yourself a glass of iced water. Add a small drop of the toffee to the water. If it firms up straight away, you are good to go. If not, keep boiling a little longer.Careful not to burn the toffeeMake sure you stir the toffee mixture regularly while it bubbles away so it does not stick and burn.It will quickly go from the stage you need it to be (145°C/300°F) to burnt. Watch the bubbling liquid gold like a hawk.Toasted flaked almondsIf you can't purchase toasted flaked almonds, they are easy to do at home and worth the effort. Place almonds on baking sheet in an oven on medium heat. Give them a mix every few minutes. Make sure to keep an eye on them as when the start to turn brown they then turn very quickly. They should toast up beautifully in around 8 minutes.