1 onion, halved and thinly sliced
25g /1 oz butter plus extra for brushing
250g/9oz chestnut mushrooms, sliced
75g/3oz button mushrooms, halved if large
12 ½ g/ ½ oz dried shiitake mushrooms
2 garlic cloves, finely chopped
½ tbsp Madeira
2 tsp fresh thyme, chopped
25g / 1oz fresh breadcrumbs
50g/2oz sunblush tomatoes, roughly chopped
25g / 1oz pine nuts, toasted
Melted butter for brushing
Firstly put the shitake mushrooms in a small bowl and cover with boiling water and leave to soak for 30 minutes. Drain (reserving the liquid) and chop any large pieces.
Fry the onions in 25g butter in a pan for 10 minutes until just softening. Add the sliced chestnut mushrooms, drained shitake and button mushrooms. Then turn up the heat and cook quite fiercely to drive off as much moisture as possible. Add the garlic and thyme for last few minutes. Stir in the Madeira, breadcrumbs, tomatoes and pine nuts then take the pan off the heat. Season well and then leave to cool.
Brush 1 sheet of filo with the melted butter and place another piece directly on top (Filo can vary in size and you need to measure it so that it is a square 30x30cm/ 12x12in). Place half of the mushroom mixture along the bottom of the square leaving a border at both edges. Roll once to cover the filling and then fold in the two sides. Brush the sides with a little more butter. Now roll up carefully until you have a nice even strudel. Repeat with another two pieces of filo and the remainder of the mushroom mixture.
Place on a baking sheet lined with baking parchment and brush with the remaining melted butter. Chill until ready to cook.
To serve bake in a reheated oven 200C / fan 180C / gas 6 for 20 minutes until golden and heated through. Serve sliced on the diagonal with the fillet of beef.
To get ahead:The strudels can be made a day ahead and stored in the fridge until needed.
To freeze:Freeze the uncooked strudels, double wrap and place in freezer bag. Defrost and cook as above, brushing with a little more melted butter.