Place chopped almonds into a pan on the stove at medium heat. Stir constantly to avoid burning and toast the almonds until they become a little darker in color and smell strongly of nuts. You can also put the nuts on a sheet pan and toast them in the oven at 350°F/177°C until they take on a little color (approximately 10 minutes). Remove the almonds from the stove AND from the pan (nuts can burn easily if left unattended while toasting or in the pan after toasting has completed). Allow nuts to cool completely. Separate the nuts for the toffee and the topping at this point to avoid accidentally adding them all to the toffee.

Place a sheet of parchment paper into the bottom of a half-sheet pan. Set a second sheet of parchment paper or a silicone sheet next to the pan.

When making caramel, timing is important so measure out all ingredients and have them prepared ahead of time.

Melt the butter in a medium saucepan (minimum 2-quart size) over medium heat. Gently stir in the sugar, water, and corn syrup using a silicone spatula until the sugar has dissolved. Add the candy thermometer to the pan and increase the heat to high. Do not stir it at this point because the caramel can crystallize if it is agitated too much.

Cook the sugar mixture until it reaches 310°F/154°C on a candy thermometer. Stir in the baking soda and salt using a clean silicone spatula. Be very careful when adding the baking soda because it will cause the caramel to bubble up vigorously. Do not get burned!

Continue to cook the caramel until it reaches 320°F/160°C. This usually takes seconds, so don’t take your eyes off it.

Remove the pan from the heat and the candy thermometer from the pan (place it on a heat resistant surface). Quickly stir in the vanilla extract and chopped, toasted almonds.

Quickly and carefully pour the toffee onto the prepared sheet pan. Use the spatula to roughly spread the toffee. Then, cover the toffee with the second sheet of parchment paper/silicone mat and use the rolling pin to smooth it out. Do not press too hard while rolling, because you can squeeze the toffee over the side of the parchment paper and burn your fingers. Allow the toffee to cool completely before removing the top sheet of parchment paper.

Begin by chopping or grating the chocolate into small pieces. Place two-thirds of the chocolate in the top bowl of double boiler. I like to use a metal bowl rather than a glass bowl because I find it helps change the temperature of the chocolate more quickly at all stages. Make sure the water is hot but not boiling. If the water is boiling, turn it down.

Heat and stir the chocolate until it is melted and reaches 110-115°F/43-46°C. I use a laser thermometer to determine the temperature and I usually take it off the heat a couple degrees before 110°F because the temperature will continue to rise after you remove the bowl.

Place the bowl on a towel to absorb any water from the bottom of the pan. Water is the enemy of chocolate and even one drop can cause it to seize. Then, add the remaining cut chocolate and stir until it becomes smooth. Continue stirring constantly until the chocolate cools to 80-82°F/26-28°C. Return it to the top of the double boiler and heat the chocolate until it reaches 87-91°F/30-32°C. This is a good working temperature for the chocolate.

Pour the tempered chocolate on the slab of almond toffee. Use an offset spatula to spread the chocolate to completely cover the toffee in a thin and even layer. Sprinkle the remaining toasted almonds over the wet chocolate and allow the chocolate to harden. While working on the topping, try to work quickly. If the chocolate is tempered correctly, it should harden very quickly (i.e., within a couple minutes) once it is poured on the toffee. If you wait too long to add the almonds, they will not stick.

After the chocolate has solidified, use your hands to break the toffee into shards. Toffee is pretty fragile, so you won’t need much force to break it. You could also hold the toffee a couple inches above the counter and drop it a few times. This should result in it breaking into shards as well.

This toffee can be stored in an airtight container at room temperature for up to 1 month, although it has never lasted that long in my house! If the toffee is left uncovered in a humid environment, it tends to get sticky and soft.