This year's first quarter-final sees the strongest five chefs from the first two heats return to battle it out in the MasterChef kitchen.First, the chefs must think on their feet in an Invention Test, in which they will create an outstanding dish showcasing nuts. They have just ten minutes to choose their ingredients from a selection of nuts, including hazelnuts, pistachios, peanuts, cashews and walnuts, flaked almonds and nut butters, as well as a range of meat, fish, fruit and vegetables, followed by 70 minutes to execute their dishes to perfection. Which of these professionals can dig deep and deliver a restaurant-standard dish with nuts as the star? Only the best will do, as at the end of the round, one chef must leave the competition.The remaining chefs must then raise their game yet again as they face the daunting task of cooking for three of the UK's most discerning restaurant critics, Jay Rayner, Leyla Kazim and Tracey MacLeod. Can they make an impression for the right reasons and deliver knockout dishes in one of the most intense rounds of the competition?Only the three most talented chefs will go through to Knockout Week and continue in the battle to become this year's MasterChef: The Professionals Champion.