Some things are obviously going to be popular. Pictures of animals holding hands/playing sports/wearing clothes. Movies with George Clooney/Brad Pitt/Matt Damon and restaurants with Keith McNally/cocktails/bright young things. Sweets involving salt/caramel/nuts are also a surefire win, and I decided to play to the crowd.
And, seriously, these bars are dangerously addictive. The first step is to make a shortbread cookie base that is buttery, a bit salty, and frankly delicious on its own. The second is to make a gooey caramel topping and mix it with salted cashews. This step can be a little tricky because caramel goes from cooked to burnt very quickly. But watching the sugar closely and stirring frequently (almost constantly) will ensure that you get a smooth, sweet caramel without any hint of bitterness.
I choose already roasted and salted cashews for ease, but you can easily roast the nuts in a 350°F oven for 6-8 minutes, then sprinkle the bars with sea salt before baking. Just don't use raw cashews, which will lack flavor and texture.
I've had people tell me that they hate me for making these—while gobbling down their second bar. I'll take it as a compliment.