📖 Instructions

1. First things first, let's get your workstation ready. Line a 9x13-inch baking sheet with parchment paper or a silicone mat. If you use parchment, a little cooking spray underneath helps it stay put. Set this aside.
2. Next, prep your almonds! Roughly chop 1 cup of almonds. You can toast them lightly in a dry skillet over medium heat for about 5 minutes until fragrant, or spread them on a separate baking sheet and toast in a 350°F (175°C) oven for 5-7 minutes. Toasting brings out their flavor, so don't skip this step. Once toasted, let 'em cool down a bit.
3. In a heavy-bottomed 3-quart saucepan (seriously, heavy-bottomed is key to prevent burning!), combine 1 cup unsalted butter (that's two sticks!), 1 3/4 cups granulated sugar, 1/4 cup water, 1 tablespoon light corn syrup, and 1/2 teaspoon salt. The corn syrup helps prevent those pesky sugar crystals from forming.
4. Attach your candy thermometer to the side of the saucepan, making sure the tip isn't touching the bottom of the pan. Over medium heat, stir constantly with a wooden spoon or silicone spatula until the butter melts and the sugar dissolves. Keep stirring!
5. Once everything is melted and smooth, stop stirring. You heard me, stop! Let the mixture come to a boil. It's going to bubble and foam, which is exactly what we want. Your job now is to simply watch the thermometer. It's a bit like watching paint dry, but with a much sweeter reward.
6. Continue to cook without stirring (just let it do its thing!) until the thermometer reads 300°F (149°C). This is the 'hard crack' stage, and it's essential for that perfect snappy toffee. This usually takes about 15-20 minutes, but it really depends on your stove and pot.
7. As soon as it hits 300°F, immediately remove the pan from the heat. Stir in 1 teaspoon of vanilla extract and about half of your toasted, chopped almonds. Be quick but careful, as it's super hot and will bubble up a bit.
8. Pour the hot toffee mixture evenly onto your prepared baking sheet. Using an offset spatula or the back of your spoon, spread it out quickly into a thin, even layer. It sets fast, so work with a sense of purpose!
9. Now, if you're adding chocolate, sprinkle the 1 cup of dark chocolate chips over the hot toffee immediately. Let them sit for 5 minutes; the residual heat will melt them. Then, gently spread the melted chocolate evenly over the toffee with an offset spatula. Sprinkle the remaining chopped almonds and the 1/2 teaspoon flaked sea salt over the melted chocolate.
10. Let the toffee cool completely at room temperature until it's hard and brittle. This could take 1-2 hours, or you can speed it up by placing it in the refrigerator for about 30-45 minutes.
11. Once completely firm, break the toffee into irregular pieces. You can use your hands or a sharp knife (be careful!). Store it in an airtight container at room temperature for up to 2 weeks. Try to resist eating it all at once!