Mix the yeast with warm water. Leave till frothy about 5 mins.
Add sugar, salt , oil and flour.
Knead well and form the dough into a ball.
Leave to rise in a greased bowl for 1 hour, keeping it covered with a damp cloth or plastic sheet.
Roll dough into two rounds, one slightly larger than the other.
Fit the smaller one into a greased shallow round pan.
Spread filling on dough and cover with the other larger round. Seal edges and flute.
Brush with egg yolk mixed with 1 tbsp. water. Sprinkle poppy seeds on top.
Bake at 200C for about 20 mins. until golden brown.
For Filling : Combine the boiled chicken , beaten eggs, grated cheese, chopped parsley, chopped capsicum, chopped spring onions, chopped celery, cream, lemon juice, chilli powder, salt , pepper and mustard.
Note : The dough is easy to roll if placed between sheets of plastic.