Preheat oven to 325°F (163°C) and line an 8x8 inch square baking pan with parchment paper, leaving an overhang on two sides.

Spread the mixed nuts on a baking sheet and toast for 8 to 10 minutes until fragrant.

In a large mixing bowl, whisk together the honey, vanilla extract, and fine sea salt.

Add the warm toasted nuts to the honey mixture and stir until every nut is thoroughly coated.

Transfer the mixture into the prepared baking pan, spreading evenly to the corners.

Place a second piece of parchment paper over the top and press down very firmly with a flat-bottomed measuring cup to compress the nuts into a tight layer.

Bake for 12 to 15 minutes until the binder is bubbling and the edges are golden brown.

Remove from the oven and allow to cool completely in the pan for at least 45 minutes to ensure the bars set.

Melt the dark chocolate chips in a microwave-safe bowl in 30-second intervals, stirring between each, until smooth.

Drizzle the melted chocolate over the cooled nut slab and immediately sprinkle with the flaky sea salt.

Refrigerate for 15 minutes to set the chocolate, then lift the slab out using the parchment overhang and slice into 12 bars.