In a food processor, combine flour, cold butter, egg, Parmesan cheese, and cold water. Process until the mixture forms a dough that sticks to the sides.

Remove the dough, wrap it in plastic wrap, and refrigerate for 30 minutes.

Roll out the dough and line a greased 24 cm tart pan with parchment paper. Prick the base with a fork and cover it with aluminum foil.

Bake in a preheated oven at 180°C for about 10 minutes until slightly cooked.

Sauté the sliced red onions in a skillet until softened. Season with salt, pepper and add honey until caramelized. Stir in the chopped green onions and set aside.

In the same pan, add a bit more olive oil and sauté the mushrooms until golden. Add the shredded chicken, cream, chili powder, dried herbs, and season with salt and pepper. Mix in the caramelized onions.

Add the cheeses to the filling and stir to combine.

In a bowl or the same skillet, mix all filling ingredients with the semi-beaten eggs.

Pour the filling over the prepared tart crust and bake in the preheated oven at 180°C for about 30 minutes until the filling is firm.