Croque Monsieur Kites

Name: Croque Monsieur Kites
Ingredients: olive oil, for greasing; 500g/1 lb (2 oz) strong white flour, plus extra for dusting; 10g/¼ oz fast-action yeast; 10g (¼ oz) salt; 80g (2¾ oz) caster sugar; 2 medium free-range eggs; 125ml (4½ oz) full-fat milk, heated until tepid; 250g (9 oz) unsalted butter, chilled; ½ tbsp olive oil; 25g (1 oz) unsalted butter; 200g (7 oz) mixed mushrooms, thinly sliced; 200g (7 oz) pancetta, 12 rashers left whole, the rest sliced into small pieces; 2 sprigs fresh thyme, leaves picked; 1 tsp finely chopped garlic; 1 tsp porcini powder (you can make your own by pulsing dried porcini mushrooms in a food processor); 150g (5½ oz) gruyère, grated; 75g (2½ oz) emmental, grated; 1 medium free-range egg, beaten with 2 tsp milk; 2 tbsp plain flour; 250ml (9 fl oz) full-fat milk; 1 tbsp wholegrain mustard; salt and freshly ground black pepper