Step 1

Roughly chop the pastry into small pieces, then transfer to a baking tray in an even single layer.

Step 2

Bake at 180C (160C fan)/350F/gas 4 for 35 minutes, stirring every 10 minutes, until golden all over, then remove and leave to cool.

Step 3

Put the dark chocolate in a heatproof bowl set over, but not touching, a pan of simmering water, and heat gently until it’s nearly melted.

Step 4

Add the coconut oil, then take off the heat and stir until fully melted.

Step 5

Set aside to cool slightly.

Step 6

For the filling, blend the pistachios in a food processor until clumpy and just starting to release their oils (you don’t want a paste, though).

Step 7

Put the white chocolate in a heatproof bowl set over, but not touching, a pan of gently simmering water until nearly melted.

Step 8

Take off the heat, stir until fully melted, then mix in in the salt, tahini and pistachios.

Step 9

Mix until it turns green and homogeneous, then stir in the crisp pastry.

Step 10

To assemble, use three-quarters of the melted dark chocolate to coat the inside of a deep two-piece silicone chocolate bar mould, making sure that it is filled deeply enough that the bar will be stable.

Step 11

Put the mould in the fridge for 20–30 minutes, until the chocolate looks dull and set.

Step 12

Spoon the pistachio filling into the mould, leaving a small gap at the top, then return it to the fridge for an hour.

Step 13

Melt the remaining chocolate again, if necessary, then pour it all over the filling, levelling the top with a spatula to neaten and seal.

Step 14

Refrigerate for at least two hours, or overnight, until fully set, then carefully unmould.

Step 15

Keep refrigerated and consume within a few days.

Step 16

The bar should be served cold, because the chocolate is not tempered.