In the last of the quarter-finals, the four best chefs from this week's heats return to face a tricky invention test. Monica and Marcus want them to create a dish that captures the essence of the forest, using an array of ingredients including meat, mushrooms and berries. There is much to prove with this dish, as the judges want to see that the chefs can produce sophisticated and innovative food.Then the chefs cook for two of the UK's toughest restaurant critics, Grace Dent and Jay Rayner. 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 two most impressive chefs will go through to the semi-finals and move one step closer to the MasterChef: The Professionals title.