I made this a few weeks ago for lunch with my sister. We hadn't quite made the switch to this horrible weather by then, so the sun was shining and with a bit of imagination we could have been in France.
I know lots of people don't like anchovies, but they really do make a difference in this recipe. Also, if you can, try to use small olives with stones, like kalamata, rather than the stoned ones you get in brine.
If you're really organised, you can cook the onions the day before, or even a couple of days before and just keep them in the fridge. They take a little while to soften, whereas the rest of the recipe is super quick.
1 tbsp olive oil
15g unsalted butter
Small bunch of thyme, leaves picked
800g onions, finely sliced
250g puff pastry (ideally the all butter type)
8-10 black olives
Heat the oil and butter in a large, heavy-based pan until the butter has melted. Add about half of the thyme leaves and the onions, and cook over a low heat for about an hour, stirring occasionally - they should be soft and slightly caramelised, but not brown. Season and leave to cool.
Meanwhile, heat the oven to 220C.
Line a baking sheet with some grease-proof paper (or you can just brush it with a little olive oil), then roll out the puff pastry until it's about the thickness of a pound coin, and place it on the baking tray.
Brush the surface of the pastry with a bit more olive oil, then cover with the cooked onions, leaving a gap of about a centimeter from the edge, all the way round. slice each anchovy in half, then arrange on top of the onions in a lattice pattern. Place the olives in the gaps between the criss-crossed anchovies. Sprinkle with the remaining thyme.
Bake for about 20-25 minutes until the pastry is puffy and golden and serve warm with some salad and bread. Yum.