Preheat oven to 300 degrees Fahrenheit.

Heat olive oil in a large saucepan over medium heat.

Sauté finely chopped onions and cubed chicken breasts in the oil until the chicken is well browned on all sides.

Add grated carrots, ground coriander, and sage to the saucepan.

Gradually stir in flour and cook for 1 minute to create a roux.

Slowly add cider, stirring constantly with a whisk to prevent lumping.

Add Dijon mustard, lemon juice, salt, and pepper to taste.

Cover the pot and let simmer over medium-low heat for 30 minutes, stirring frequently to prevent sticking.

Add sliced mushrooms and half-and-half.

Cook for 10 minutes, allowing the mushrooms to soften and the sauce to thicken.

Allow the mixture to cool slightly.

Place one pie crust into a pie pan.

Add the chicken and vegetable mixture to the pie crust.

Cover with the second pie crust.

Make holes in the top crust to allow steam to escape.

Brush the top of the pie with beaten egg.

Bake for about 30 minutes, or until the crust is golden brown and the filling is heated through.