Roll puff pastry into a 28cm circle 5mm thick on a floured surface.
Maintain pastry on document-lined tray and chill for one hour.
Simmer onions in cider, vinegar, and sugar for 10-13 minutes total until soft.
Char the cooked onions using a blowtorch or hot grill and let cool.
Preheat oven to 220°C.
Prick pastry, brush with egg yolk and cream mixture, and bake for 20 minutes.
Reduce heat to 110°C and dry pastry for 15 minutes.
Increase oven temperature to 180°C.
Coat steak strips in cornflour and fry in oil for 6-8 minutes until crisp.
Brush pastry with beef extract, layer with marmalade and beef, then warm in oven.
Whisk crème fraîche, blue cheese, and chives together to make a dressing.
Drizzle dressing over the warm pizza and garnish with watercress.