Make a smooth batter by whisking the milk, eggs and flour together. Heat a small amount of oil in a frying pan. When it is hot, add the right amount of batter to make a very thin layer in the bottom of the pan. Cook until golden on the underside, then flip the pancake over and cook the other side. Repeat this process until all the batter has been used and set the cooked pancakes to one side
Quickly blanch the spinach leaves in boiling water and then add to iced water to cool. Remove the leaves and ensure that they are dried thoroughly
Place a sheet of cling film onto a board and lay 3 pancakes onto it. Ensure that the pancakes fully cover the cling film, overlapping where necessary. Add a single layer of spinach leaves on top of the pancakes and spread the mushroom duxelle evenly over the spinach. Lie the beef on top and wrap the pancakes, spinach and mushrooms tightly around the fillet
Spread the mushroom duxelle evenly over the spinach and add the beef on top. Wrap the pancakes, spinach and mushroom mix around the Beef in the cling film, making sure they are wrapped tightly and are fully sealed. Leave in the fridge to rest, overnight if possible
Roll out the puff pastry into a thin sheet about 1/4 cm thick – it will need to be rolled thinner if the pastry is pre- rolled
You will need 400g of puff pastry