Leftovers should be an easy job, right? You should take said leftovers and turn them into something nice to eat in no more than a heartbeat. Or you could do it the not so easy way.

For the leftovers, I had some roasted duck breast we’d had for Christmas Eve dinner that was a shame to let go to waste, of course. And I thought of making sandwiches, because I remembered having an excellent one at a food market in London this Summer. It was our first day in London, we had gone out for a stroll around the block and we just landed in the middle of a food fair. We passed by all the vendors, but what really caught my eye was an attractive looking sandwich cart ran by two French guys. They only had about three or four choices scribbled on a chalkboard, but everything looked and smelled great. I went for the Roquefort and Duck Sandwich and it was a great choice: perfectly roasted shreds of meat tucked between layers of caramelized onions and Roquefort, all pressed between a pain de mie bun.

I’m not very fond of store bought hamburger buns and I find making them a bit too difficult. On the other hand, I love focaccia and it’s also a breeze to make, so I thought of recreating the sandwich with that instead of buns. I used Julia Ziegler-Haynes’ recipe, that is absolutely perfect.

What I love about foccacia is that it’s crisp on the outside, moist on the inside and it has the most wonderful olive oil flavour. I don’t make it as often as I’d like, so when the opportunity arises, I jump.

These sandwiches aren’t difficult to make, you just have to have a little bit of patience with the onions and if you like, you can always substitute focaccia for whatever kind of bread or buns you like.

For the focaccia:

7 cups all-purpose flour

2 tsp active dry yeast

3 cups water

3/4 cup olive oil

2 Tblsp sea salt

In the bowl of a stand mixer fixed with the paddle attachment, combine the flour and the yeast and mix well. Alternately you could use a hand-mixer. Pour the water and stir unti incorporated and the dough comes together sticky and wet. Take out and move to a big bowl, drizzle half of the olive oil on top of the dough and place a clean, damp cloth over it. Put the bowl in a warm place and leave to rise for about 3 hours, until it has doubled in size.

Coat a 40x30cm/18”x13”in roasting tray with the rest of the olive oil. Pour the dough onto the tray. Spread your fingers wide and press the dough down and outward, with your hands flat. Do not poke it and make sure to spread the dough until it reaches the edges of the tray.

Heat the oven to 225C/450F. While the oven is heating, leave the dough to rise a little bit more in the tray. Sprinkle the dough with the coarse sea salt and pop it in the oven for about 30 minutes, until golden-brown.

For the Roquefort spread:

1/2 cup crumbled Roquefort

1/4 cup sour cream

In a small bowl, mix together the Roquefort and the sour cream until well combined.

For the caramelized onions:

2 large onions

15gr/1Tblsp unsalted butter

1Tblsp olive oil

2Tblsp balsamic vinegar or red wine

Salt

Halve the onions lengthwise and remove the skins; cut up the ends and slice into half-moons, from root to stem. Place a skillet over medium heat and melt the butter with the oil. Add the onions to the skillet, stir to cover with the mixture of butter and oil. Cook for 20-30 minutes, until caramelized and jammy. At this point you will need to deglaze the pan, by pouring the vinegar or the wine over the onions. As it starts to bubble, scrape up the fond and stir it into the onions. Salt the onions to taste.

Please note that caramelized onions can be tricky. I recommend you cut the onions a little big bigger than you would usually and use a small skillet, so that the onions stay together,  as they tend to burn faster if they are spread out.

If you’re making this from scratch, this is what you could do about the duck:

4 duck legs

salt and pepper to taste

6 cloves of garlic, crushed

2 Tblsp dried rosemary

1 cup red wine

Preheat oven to 180C/375F. Score the skin with a knife, then place in a roasting pan. Sprinkle with salt and pepper. Add all the rest of the ingredients and roast for around 90 minutes, turning the legs halfway through. Once they’re done, remove from the oven and take out of the pan. When the duck is cool enough to handle, shred the meat.

To assemble the sandwiches:

Slice your focaccia (or bun) and slather Roquefort and sour-cream mixture on the bottom half of the bread, add shredded meat, top with caramelized onions and a salad leaf (if you don’t have any, that’s ok, it’s just as good without it). Place the top half of the bread over and dig in! If you’ve opened a bottle of red for the onions and the duck, pour yourself a glass as well, it goes great with this sandwich.