Preheat oven to 350 degrees Fahrenheit.

Para-bake the pie crust for about 8 minutes.  Allow the crust to cool down before adding any other ingredients to it.  Put the pie crust on a baking sheet with foil on it.  This will save you clean up later.  

In a large pan on medium heat, cook the bacon until it is crispy-ish.  You want it slightly crisp but not dry.  Remove the bacon from the pan and crumble or chop.  Add the crumbled bacon to the pie shell. Do not drain the fat from the pan. 

Lower the heat to a low-medium and add the onions.  Cook until the onions soften and begin to caramelize. 

To the same pan, add the butter, the mushrooms, and 1/4 teaspoon of the salt.  Cook until the mushrooms have reduced in size and have released most of the water.  It will take about 8 minutes.  

Stir the dill and chives into the mushroom mixture.

Remove the mushroom mixture from the stove and allow it to cool down for a minute.  Once at room temperature, add the mushroom mixture to the pie shell.

Top the mushroom mixture with the cheeses.  

In a bowl, beat the eggs and heavy cream, along with the remaining salt.  Pour the egg custard mixture in the pie shell. 

Bake for about 40 to 44 minutes, or until the quiche is set the the top is golden.  Enjoy warm or at room temperature.