Method

• 1.
  Preheat oven to 200°C/180°C fan-forced.
• 2.
  Heat a large, deep cast-iron frypan over high heat. Heat 2 tbs of the oil and the field mushrooms. Cook, tossing frequently, for 5 minutes or until golden and all liquid is evaporated. Transfer to a large heatproof bowl. Return pan to heat. Once pan is hot again, heat another 2 tbs oil and add the button and Swiss brown mushrooms. Cook, turning occasionally, for 5 minutes or until golden and all liquid is evaporated. Transfer to bowl.
• 3.
  Repeat process once more with remaining oil and portobello mushrooms. Cook, turning occasionally, for 5 minutes or until golden and all liquid is evaporated. Transfer to bowl and set aside.
• 4.
  Reduce heat to medium. Add the butter and onion to same pan. Cook, stirring constantly, for 2 minutes until light golden and starting to soften. Stir in wine, most of the thyme leaves (reserve 1 tbs for serving) and extra thyme sprigs and simmer, stirring occasionally, for 3 minutes or until wine reduces by two-thirds.
• 5.
  Stir in the flour and cook, stirring constantly, for 1 minute. Stir in cream (reserving 2 tsp) and garlic, then return all mushrooms and any resting juices to pan. Stir to combine and until mixture comes to a simmer, then remove pan from heat. Season heavily with salt flakes and freshly ground black pepper (mushrooms can take a good seasoning).
• 6.
  Top mushroom mixture with pastry, trimming away excess. Prick pastry a few times with the tip of a knife, then brush with the reserved 2 tsp cream.
• 7.
  Transfer to oven and place a large baking tray on a separate shelf underneath to catch any overflowing sauce. Bake for 35-40 minutes until pastry is deep golden, puffed and cooked. Remove and stand for 5 minutes.
• 8.
  Serve sprinkled with reserved thyme leaves and radicchio alongside, if desired.