It really amuses me when things which are actually relatively simple to make - for example, sea salted caramel/toffee/chocolate - become trendy in a way which seems intimidatingly gourmet. Toffee (and other sugar-based candies like marshmallows and butterscotch) are suprisingly easy - and the addition of a dark chocolate and a sprinkle of sea salt makes for an impressive-looking gift. It does take a bit of patience and probably a few botched batches before you perfect it, but when I say simple, I mean simple.
What you need for a basic butter tofffee is:
• 1 cup butter
• 1 cup sugar
• a stove, a saucepan, a wooden spoon, and a large piece of aluminum foil on a hard heatproof surface
Good butter really does make a difference here - you’ll taste and see the difference between something like Plugra and your standard grocery brand. I prefer salted butter, but you can always add a pinch of salt to the mix if you’ve only got sweet. Let the butter warm up to room temperature (sudden temperature changes will result in separation or graininess) and add it to a saucepan with the sugar, and a teaspoon or so of water to help them melt together.
Make sure the butter melts very slowly over medium-low heat, stirring the whole time to ensure the sugar dissolves and melts evenly. (A gas stove makes this MUCH easier, but it’s not impossible with an electric.) Slowly raise the temperature to medium and continue stirring slowly - the mixture will begin to bubble as the water boils off. If at any point the toffee begins to separate or appears grainy, remove it from the heat, add a few spoons of hot water, and stir vigorously until it comes back together, then gradually heat it up again. (A reliable stove, a heavy pan, and good butter will help prevent this as well.)
A candy thermometer helps a lot here - reading up a bit on the science of how sugar and butter melt, carmelize, and burn is very helpful too, and to be honest, screwing up a few batches will teach you more than reading. For a hard, crunchy toffee, you should remove the mixture from the heat as soon as it reads around 300 degrees F. (Above this it will turn into a sizzling burnt liquid which will not solidify again, and below will be somewhere between a nougat and chewy butterscotch.) Once you’ve done this a few times you can probably ditch the thermometer - it’s easy to recognize the stage of caramel from the colour and texture and from simple water tests (which is where the stage names like “soft ball” and “hard crack” actually come from.)
As soon as you remove the toffee from the heat you may want to stir in some flavoring - a tablespoon of vanilla, rum, amaretto, or another liquor goes a long way. Stir quickly until the alcohol evaporates, and then pour the mixture (which will rapidly be thickening) smoothly on to a sheet of aluminum foil. Smooth a bit with a spatula if necessary.
After the mixture begins to harden (about 3 minutes), sprinkle it with finely chopped chocolate (dark, bitter chocolate is best to counteract the sugary candy, though you may also want to try a mixture of dark and milk or dark and white.) The chocolate will melt within a few minutes and you can use a spatula to spread it into an even layer. Before the chocolate hardens, sprinkle it lightly with a few pinches of coarse salt, and set it aside for an hour or two to cool and harden. Then break into pieces and enjoy!