Process:

Prepare the shortcrust pastry dough:

1. Rub together flour, salt and cold butter to breadcrumbs consistency.
2. Add in sesame seeds and poppy seeds, mix lightly.
3. Add water gradually and bring together the dough.
4. Wrap in cling film and rest in fridge for few hours, minimum 30 minutes.

Shape & bake the shortcrust base:

1. Preheat oven to 180°C.
2. Roll out the pastry dough to about a half cm thinness on a floured surface, bigger than the tart case to form the sides.
3. Ease into a 24cm tart case carefully, using a rolling pin to transfer the pastry.
4. Repair tears in the pastry, if any, using excess pastry.
5. Rest the pastry in the fridge for another 30 minutes.
6. Line with butter paper and fill with pie weights/ beans/ rice.
7. Blind bake for 25 minutes, 15 with the weights and 10 without them.
8. Remove out of the oven and cool for 10-15 minutes before adding in the filling.

Make the caramelised onions:

1. Heat up a wide pan on medium heat.
2. Add the butter and oil.
3. Once the butter is melted, add the sliced onions and salt. Give it a good mix.
4. Cook covered on medium-low heat and stir occasionally to get an even brown colour.
5. Add a splash of water if the onions are sticking to the pan. and mix well to incorporate the caramelised bits from the pan.
6. Finish with a sprinkle of mustard powder and give it a good mix.
7. Switch off heat once deep brown caramelised onions are obtained. This should take about 15 to 20 minutes.

Make the sautéed mushrooms: 

1. Sauté garlic in olive oil for 2-3 minutes on medium heat.
2. Add in the sliced mushrooms and mix well.
3. Cook until all the water given out by mushrooms has dried and the mushrooms have picked up a golden brown colour.
4. Season with salt and pepper; give it a mix.
5. Take off the heat and add in the chopped chives.

Prepare the savoury custard:

1. Whisk together the eggs, cream and milk in a large bowl.
2. Season with salt and pepper, and set it aside.

Assembling the quiche:

1. Preheat oven to 160°C.
2. Fill cooled shortcrust base with caramelised onions in an even layer.
3. Spread sautéed mushrooms evenly next.
4. Dot the cream cheese evenly across the quiche.
5. Place the tart case onto a baking tray and place it in the oven halfway with the door ajar. Pour the savoury custard into the shortcrust base carefully and then place the baking tray fully in the oven.
6. Bake for 40-45 minutes, till the centre has a slight wobble.
7. Remove into a wire rack and cool for 30 minutes, and serve warm or at room temperature.