To make pie crust, combine wheat flour and butter cubes using your fingertips until the mixture resembles breadcrumbs. Add in ice water in batches and knead until a soft dough is formed. Wrap and chill for 30 minutes.
Lightly grease the baking tray. Roll out the dough and put it on the tray, use a fork to gently prick the dough. Bake in preheated oven at 180°C for 12 minutes.
To prepare filling, in a mixing bowl whisk egg, milk, cream, Knorr Concentrated Chicken Stock, Knorr Pasti Sedap, black pepper and garlic until well combined. Add in the mushrooms, spinach and cheese. Mix well and pour into cooked crust.
Bake quiche in a preheated oven at 180°C for 20-25 minutes until the custard is just set.