Working in batches, place the mushrooms into a food processor and pulse until finely chopped. Transfer to a bowl. Heat the butter in a large frypan over medium heat. Add the shallots and a pinch of salt and cook for 5 minutes until soft. Add the garlic and thyme and cook for a further 1 minute until fragrant. Increase heat to medium-high. Add all the mushrooms and cook down for 20 minutes until there’s no moisture left in the mushrooms and the pan is dry. Add the port and cook down until the wine has completely evaporated (this step is very important to avoid soggy pastry so if it needs longer, keep cooking). Season with salt and pepper and transfer to a tray to cool completely.
Meanwhile, wipe out the frypan with paper towel and place over a medium-high heat. Pat-dry beef fillet with paper towel and season well with salt and pepper all over. Add the oil to the frypan and brown the beef fillet all over, turning often, until sealed. Transfer to a plate to cool.
Lay 2 or 3 large pieces of cling wrap onto a clean bench, overlapping to make a 40 x 40cm square, larger is fine. Lay the prosciutto vertically onto the cling wrap, slightly overlapping, to make a rough rectangle shape of 30 x 40cm. Spread the mushroom mixture over the top of the prosciutto, using an offset spatula to spread out the mixture evenly, pressing down firmly. Spread the pâté over the bottom of the beef fillet and place horizontally in the centre of the mushroom covered prosciutto. Spread the remaining pâté over the beef to cover completely. Use the cling wrap to lift up the prosciutto and mushroom layers over the fillet to encase into a tight log. Wrap tightly in cling wrap by rolling it up and securing the ends. Transfer to the fridge for 4 hours or overnight.
The next day, on a lightly floured bench, roll out the pastry to 30 x 35cm and brush with the egg yolk mixture. Unwrap the beef from the cling wrap and place it in the centre of the pastry. Roll up the pastry tightly and tuck in the ends, pressing firmly to seal. Trim off any excess pastry and use a leaf cutter to cut out pastry pieces to decorate the top. Line a baking tray with baking paper and place the wellington seam-side down. Brush all over with egg yolk mixture. Place pastry leaves over the top and brush with more egg. Transfer to the fridge for 1 hour to chill the pastry.
Preheat oven to 180°C Fan.
Sprinkle with salt and bake the beef wellington for 50 minutes, or until the internal temperature reaches 45°C on a meat thermometer. Transfer the wellington to a cooling rack and allow to rest at room temperature for 25-30 minutes to allow the meat to finish cooking and relax the beef (the internal temperature will continue to rise, but this is what you want). Transfer to a board and cut into thick slices to serve.Recipe, Food Styling and Photography by Karen McFarlane, foodlove.com.au
1kg Swiss brown mushrooms
60g unsalted butter
2 shallots, finely diced
2 cloves garlic, finely chopped
1 tsp finely chopped thyme
½ cup port
1 tbs olive oil
1kg trimmed beef fillet, centre cut so the fillet cooks evenly
6 thin slices prosciutto
375g puff pastry
2 egg yolks, beaten with 1 tsp water
sea salt & cracked black pepper