1. Cut the eye fillet into strips, approximately 2.5 – 3cm in diameter and then season the strips with salt and pepper.
2. Heat a frying pan with olive oil and once smoking, sear the beef on all sides (note: you are just forming an outer crust on the beef, not cooking through). Remove from the pan and set the beef aside.
3. Heat a little more oil in the pan and add the sliced mushrooms. Cook the mushrooms until they are dry (mushrooms leach quite a bit of moisture when cooked so you want to cook for long enough that all the liquid has evaporated and the mushrooms have reduced substantially in size). Stir through the chopped thyme right at the end of cooking and then leave the mushroom mixture to cool.
4. Blend the mushrooms in a food processor until smooth.
5. The next stage is similar to when making sushi. Dust your bench with a little flour and roll the pastry sheet even thinner – approximately 1-2mm in thickness. The thinner the better, but try to keep it in a square or oblong shape.
6. Spread a thin layer of the mushroom mixture on the pastry; start at the end of the pastry which is closest to you and cover an area 6cm in length by the width of your pastry but leaving a boarder of a couple of mm each side. There should be an adequate amount of mushroom mixture spread on the pastry to completely encase the beef.
7. Brush your beef strips with the Dijon mustard and place them lengthways in the centre of the mushroom mixture. Wrap the pastry around the beef, trim the excess pastry, press the ends together and then place the Wellingtons on a baking sheet lined with baking paper. Refrigerate until you are ready to cook.
8. Preheat your oven to 200ºC on Bake.
9. Brush your Wellingtons with egg wash and place into your preheated oven for approximately 8 minutes (you want to cook your pastry and have medium to medium-rare beef).
10. Remove from the oven, rest for a few minutes on a chopping board and then slice into bite-sized rolls.
11. Serve the little Wellingtons immediately, on their own or with a tomato relish.