Take the pastry out of the fridge 30-45 minutes before you want to use it – this just allows it to warm and soften a little so it won’t crack on unrolling.
Once the pastry has come to room temperature, unroll it onto the worktop. Use a small sharp knife to slice it into 6 equal square-ish pieces. Take a piece and lift it into one of the holes in the muffin tin, crimping and pressing it down to the base but leaving the frilled edges proud of the tin to contain the filling. Repeat with the other pieces of pastry then slide the tin in the fridge to chill for half and hour – this will help prevent the pastry shrinking when you cook it. so the filling
Whilst the pastry is chilling, make the filling. Add the raisins to a small bowl and pour over boiling water to cover. Leave to soak for 30 minutes before draining well.
Meanwhile add the brown sugar and butter to a bowl and beat until smooth and creamy with an electric whisk. You can also use a food mixer, or do it by hand with a wooden spoon and a bit of elbow grease. Add the egg, syrup, vanilla and salt and beat until smooth.
Remove the tin from the fridge and divide the drained raisins between each pastry case then pour over the filling mixture. Side the tin back into the fridge whilst you light the barbecue.
To bake in a barbecue you need to create and oven-like heat, so you cook using convection (or hot air) currents rather than the direct heat from the fire. The best way to do this is to light two small charcoal fires, one on either side of your barbecue, with a generous fire-free zone in the middle. you will need a barbecue with a lid you can close to trap the hot air inside.
Once the barbecue is hot (aim for a temperature of around 200C) set the tin of tarts in the centre between the two fires and shut the lid. Bake until the filling is just set and the pastry is golden – around 30 minutes, depending on the heat of your fire. The filling may ooze up and out a little. Allow to cool a little before easing from the tin. Serve warm or cold, sprinkling with a just a few extra flakes of Maldon just before eating.
To cook inside:
Pre-heat your oven to 200C fan temp and bake for around 20 minutes. These tarts cook slightly quicker in a conventional indoor oven.