Snap the dark chocolate into a large mixing bowl.
Cube and add the butter, then tip in the sugar.
Microwave in 30-second blasts on a medium heat (600W), stirring every time, until the chocolate has completely melted.
Fold in the flour with a pinch of sea salt, then crack and beat in the egg.
Divide up the mixture between 4 small microwave-proof cups.
Break the chocolate bar into chunks and push into the mixture.
Microwave in pairs on high (800W) for 1 minute 15 seconds, or until risen and gooey in the middle.
Remove the cups from the microwave (be careful – they’re hot!) and leave to cool slightly.
Drizzle with the double cream or dollop over the crème fraîche and enjoy straight from the cups.
