Arrange a rack in center of oven; preheat to 180°C. Line a 30 x 20cm dish with baking paper, leaving an overhang on all sides.

In a large bowl, using a handheld mixer, beat 1 cup butter, 3/4 cup brown sugar, and 1 sachet Society Coffee Cappuccino Caramel Toffee until smooth and creamy. Beat in egg yolk until just combined. Add flour and salt and beat on until just combined.

Transfer mixture to the dish, pat down in an even layer, and refrigerate until firm, 5 to 10 minutes.

Sprinkle crushed pretzels over, then gently press into dough. Bake shortbread until lightly golden brown around the edges, about 22 minutes. Let cool slightly.

Meanwhile, in a small bowl, combine vanilla and 1 sachet Society Coffee Mochaccino. In a large pot, cook milk, honey, and remaining 1/2 cup butter and 3/4 cup brown sugar, stirring constantly and scraping bottom and sides of pot, until mixture is very thick, a bit darker in colour, and beginning to pull away from sides and bottom of pot, 3 to 5 minutes.

Immediately remove from heat and whisk in cappuccino mixture until combined. Pour over shortbread, smooth in an even layer, and let cool. Refrigerate until caramel is firm to the touch, about 15 minutes.

Meanwhile, microwave chocolate and oil in 20-second increments, stirring between each, until melted and smooth, about 1 minute total.

Pour chocolate mixture over cooled caramel and spread in an even layer. Sprinkle with sea salt and continue to refrigerate until firm, 20 to 30 minutes.

Using baking paper overhang, lift out bar and transfer to a cutting board and cut into squares.