Place the all-purpose flour in a mixing bowl.

Add the salt and mix until combined.

Cut the unsalted butter into very small pieces.

Add the sour cream and combine thoroughly.

Wrap the dough in plastic cling film and chill in the refrigerator for 1 hour.

Rinse the chicken breast, cut into strips, and then small pieces. Place the chicken pieces in a bowl and sprinkle with kosher salt and freshly ground pepper. Toss to season evenly.

Heat the canola oil in a large skillet. Add the chicken pieces and stir-fry them until are almost cooked through.

Add the mushrooms, sage, prunes, and parsley and stir to combine. Cook for about 5 more minutes, until the mushrooms start to soften a bit. Remove from heat and set aside.

Crack the eggs into a separate bowl, add the cream, and whisk together. Season with kosher salt and freshly ground black pepper.

Preheat oven to 325 degrees F.

Grease and flour a 12"tart pan.

Remove the tart dough from the refrigerator.

turn out the dough onto a lightly floured work surface and roll out into a circle.

Transfer the dough circle to the prepared greased pan and use your fingers to crimp the edges all around the pan to form the crust. Use a fork to poke several holes in the bottom of the crust.

Evenly distribute the chicken, mushroom, and prune mixture inside the pan.

Pour the egg and cream mixture into the pan over the filling.

Sprinkle the ground nutmeg evenly over the top.

Place in the oven and bake for 40 minutes or until the tart has solidified and the crust starts to turn golden brown.

Remove from oven and let cool until it is just warm to the touch.

De-pan the tart and serve.