Place all the dough ingredients in a bowl.

Mix or knead the dough together - it should be soft.

Wrap the dough in plastic wrap and let it rest for 30 minutes in the fridge. This is important as an adequate resting time is crucial for the final consistency of the baked tart crust.

Roll out the dough thinly or press it into a greased tart form.

Prick it with a fork and pre-bake the tart crust for 10 minutes at 200 degrees Celsius (392 degrees Fahrenheit).

Take the pre-baked tart crust out of the oven and add the filling to it.

 

Clean the mushrooms and slice them.

Slice the red onion and spring onions.

Heat a pan with oil and add a knob of butter when the pan is hot. 

Sauté the mushrooms, onions, and spring onions in the pan for a few minutes until everything is slightly wilted.

Whisk together eggs and cream and season with salt and pepper as needed.

Sprinkle the pre-baked tart crust with about 1/3 of the grated cheese.

Then, add the vegetable filling over the cheese in the crust and pour the egg mixture over.

Finally, sprinkle the tart with the remaining cheese.

Bake the tart for about 30 minutes at 200 degrees Celsius (392 degrees Fahrenheit), until the egg mixture is set, and the surface is beautifully golden.

Serve the warm tart with a green salad on the side.