This year's first quarter-final sees the four strongest chefs from the first two heats return, ready to up the ante and impress Monica Galetti and Marcus Wareing in two tough challenges.First is an Invention Test, with Marcus and Monica asking the chefs to create a dish based on the set theme of spices. They will be presented with a market containing a variety of ingredients to choose from, including an eclectic range of spices. The chefs must now be resourceful, working to the best of their ability and demonstrate the know-how to incorporate and highlight spice throughout their dish.Next, the four professionals face the challenge of cooking for two of the UK's most discerning restaurant critics, Jimi Famurewa and William Sitwell. They have one hour and 15 minutes to wow the judges with a two-course menu that's memorable for all the right reasons.Only the three most talented chefs will go through to the semi-finals and continue their attempt to win the MasterChef: The Professionals title.