Directions

1. Season the lamb fillets with salt on all sides. In a hot cast-iron pan with the peanut oil, sear the lamb on all sides until nicely coloured. Remove from the pan and let cool on a resting tray.
2. Finely dice the mushrooms either in a food processor or by hand, taking care not to create a purée. If using a food processor, use the pulse function.
3. Melt the butter in a frying pan over medium-high heat. Add the mushrooms and rosemary, season with salt and pepper, and cook until the mushrooms have released their moisture. Deglaze with brandy and reduce until evaporated. Remove from heat, adjust seasoning, and cool in the fridge.
4. For the crêpes, whisk together the flour, milk, and 2 eggs to form a smooth batter. In a non-stick pan with a little oil over medium to medium-low heat, pour in enough batter to cover the bottom. Cook until set, then flip and cook for another minute. Remove and let cool on a rack.
5. To assemble the Wellington, lay out cling film, place a layer of crêpes, followed by prosciutto, and then spread a layer of the mushroom mixture (duxelles), trimming any excess. Brush the cold lamb fillet with mustard and place in the centre of the duxelles. Roll all the layers together tightly in cling film and chill in the fridge for at least 1 hour.
6. Lay one sheet of pastry on a bench, place the chilled lamb roll from the fridge on top, then cover with another sheet of pastry. Press the edges to seal tightly, trim any excess, and wrap tightly in cling film. Chill again for 1 hour.
7. Remove from the plastic, brush with a beaten egg, and bake in a preheated oven at 180°C (356°F) for 30 minutes. Rest for 10 minutes before slicing and serving. Sprinkle with flaky sea salt to finish.