Preheat oven to 325 degrees F. Line an 8-inch square baking pan with parchment or foil, making sure to leave a bit overhang on either side. This will make it easier to pull the bars out of the pan later on.

In a large bowl, beat together the butter and sugar until light and fluffy, about 2 minutes. Add the flour and salt and beat on low until just combined. Pour out into the prepared pan and press down firmly into an even layer. Bake until lightly golden brown, about 30 minutes. Transfer to a wire rack and set aside to cool completely.

To make the caramel, in a medium saucepan, combine the condensed milk, butter, syrup and salt. Cook the mixture over medium heat, stirring often with a rubber spatula, until thickened and becomes a deep brown golden color, about 10 to 20 minutes. Keep an eye on it and keep stirring so that the bottom doesn't burn. If you find that it's sticking a lot, lower the temperature to keep it from scorching. Remove from the heat and stir in the vanilla extract and cashews until well combined. Immediately pour over the cooled crust and spread out into an even layer.

Place the chocolate chips in a heat-proof bowl and microwave in short bursts until melted through and smooth. Pour over the caramel and spread out into an even layer. Sprinkle with coarse salt on top and chill in the fridge until firm, at least 1 hour. Remove the bars from the pan and then cut into even pieces with a sharp serrated knife. Leftovers can be stored in an airtight container in the fridge for up to 3 days. Enjoy!