Preheat your oven to 200C.
Start by making your vol au vent pastry cases. You need 2 round pastry cutters, 1 of them about 1-1.5cm smaller in diameter than the other. Roll your pastry to approx. 5mm thick and use your bigger cutter to cut out circles of pastry. Egg wash these, then use the smaller cutter to create an indent half-way through the pastry. Bake on a tray for approx 10mins until risen and golden brown. Cool, remove the lids and scrape out the soft pastry from inside.
Dice your chorizo, caramelise over a medium heat, then set aside to cool.
Use a clean cloth to ensure your scallops are dry, then place a clean, heavy based frying pan over a medium-high heat.
Season your scallops with fine sea salt, then place the larger side face down into the pan. Once they have stuck, add 1-2 tbsp oil and pan fry until golden brown. Flip them over, add the butter, turn the heat down to low and baste briefly.
Remove from the heat, roughly dice the scallops, then add back to the pan and combine with the chorizo and parsley, and season with salt and pepper.
To assemble, place a small teaspoon of crème fraîche into the bottom of each vol au vent, fill with the scallop and chorizo mix, and top with the pastry lid.
Serve immediately.