- In a pot over medium-high heat, brown the leek and onion in the butter. Add the wine and let reduce by half. Add the broth. Bring to a boil and simmer until reduced by three-quarters. Strain through a sieve, pressing firmly with the back of a ladle to extract all the flavours. Return the sauce to the pot and set aside.
- In a small bowl, combine the cornstarch and water. Gradually pour the cornstarch mixture into the sauce, whisking constantly. Bring to a boil and simmer for 1 minute or until the sauce has thickened slightly. Season with salt and pepper.
After preparing our recipe for duck breast with roasted leek and onion (see recipe), you will have leftover leek and red onion scraps. Keep them for preparing this sauce: a great way to prevent food waste!