Pulse the crust ingredients in the food processor until crumbly. Transfer to a parchment lined work surface and form into two discs. Wrap in plastic and chill for several hours.
Saute the mirepoix in the butter over medium heat, seasoning with salt and pepper. Add the soup and stir until well combined.
Preheat the oven to 375 degrees. Roll out each dough disc large enough to fill a pie plate and then cover the filled pie. Place one dough sheet into the pie plate. Line the crust with the Swiss cheese. Fill with the chicken mushroom filling. Top with the second crust, trimming any edges. Glaze with egg wash and sprinkle with rosemary salt.
Bake for about 35 minutes, until the crust is golden brown.
*For a gluten free crust, use a gluten-free flour mix and add one additional egg.