It's the quarter-final, and the best four chefs from this week's heats return to face two more daunting challenges set by judges Monica and Marcus. The one that fails to cut the mustard will have their MasterChef dream shattered as they leave the competition.To start, it's the infamous Invention Test as the four quarter-finalists are asked to prepare and cook a standout tart – a sweet or savoury pastry treat that will blow the competition out of the water. To pile on the pressure, they also need to dish up the perfect accompaniment - a side dish which compliments the flavours of the main event without stealing its thunder. Creativity can run wild as the chefs raid the MasterChef larder for the perfect ingredients to accompany their pastry show-stopper.Next, they are subjected to one of the most feared of all MasterChef rounds - cooking their own two-course menu for three of the UK's most experienced food critics, Tom Parker Bowles, Jimi Famurewa and Grace Dent. They have just one hour and 15 minutes to turn out four identical portions of each dish that delivers on every front.The three chefs who impress the most will earn their place in Knockout Week, leaving them one step closer to achieving the goal of becoming MasterChef: The Professionals champion 2023.