Mound the flour on a surface and make a center well.
Combine the butter and salt in the well by hand.
Mix in iced water until the dough is grainy and marbled.
Wrap the dough ball in film and chill for 20 minutes.
Roll the pastry into a 40x20cm rectangle on a floured surface.
Fold the pastry into thirds and rotate a quarter-turn.
Roll into a rectangle again, fold into thirds, and chill for 30 minutes.
Repeat the rolling and folding twice more, then chill for 30 minutes.
Whisk the pancake eggs and flour together in a bowl.
Gradually whisk in the milk to form a smooth batter.
Fry two pancakes in butter until golden-brown on both sides.
Fry the mushrooms in butter for 4 minutes and season well.
Preheat your oven to 200°C.
Sear the seasoned beef in a hot pan until browned.
Layer pancakes, pâté, mushrooms, and spinach over the rolled pastry.
Brush with egg, wrap the pastry around the beef, and seal.
Place the Wellington on a tray, brush with egg, and chill for 30 minutes.
Brush the chilled pastry with egg one final time.
Bake at 200°C for 25 minutes for rare or 35 minutes for medium.
Boil the broccoli in water for 4 minutes.
Drain the broccoli and fry in oil for 3 minutes.
Reduce the beef stock by half, add wine, and reduce again.
Slice the Wellington and serve with broccoli and jus.