Method To make the pastry, put sifted flour into a mixing bowl and rub in butter (or process flour and butter until mixture resembles breadcrumbs). Add egg yolk and enough water to make ingredients cling together (or process until ingredients just come together).
Press the dough into a ball and knead lightly on a floured surface until smooth. Wrap in plastic and refrigerate for 30 minutes. Roll out the pastry dough between 2 sheets of baking paper until large enough to line a lightly greased loose base flan tin. Trim the edges and refrigerate for 30 minutes. Cover pastry with baking paper and fill with dried beans or rice. Bake in preheated oven at 200°C for 10 minutes. Remove beans or rice and paper; bake further for 10 minutes or until lightly browned. Cool.
To prepare the filling, heat butter or margarine, add garlic and fry until fragrant. Add chicken and button mushrooms and fry until cooked through.
Dish out and mix with straw mushrooms and capsicum. Drain on a colander and leave aside to cool. Spread this mixture onto the pastry case.
For the custard filling, combine egg, milk, pepper and salt well together. Pour into the pastry case to cover the mushroom filling. Bake in preheated oven at 180°C for about 25–30 minutes or until mixture is set and cooked. Serve quiche hot.