Overview: This quarter-final sees the six most talented chefs from the week's heats set out to impress Monica and Marcus in two high-stakes challenges. First up, the chefs face an invention test, featuring a particular ingredient. This week, Monica has selected a favourite, found at the heart of many cuisines - the onion. The professionals are under pressure when faced with a whole host of varieties of onion and a huge array of other ingredients. They need to focus and rapidly find inspiration to cook a dish in 70 minutes that will deliver flavour, finesse, sparkle, and an inspired approach to the onion. At the end of the challenge, two contestants leave the competition