- Prepare the dough by combining flour, sugar, and salt in a food processor. 
- Add cubed butter and pulse until it resembles small peas. 
- Gradually add ice-cold water, mixing until the dough comes together. 
- Wrap the dough in plastic wrap and chill for at least an hour. 
- Preheat your oven to 375°F (190°C). 
- Roll out the chilled dough on a floured surface to fit your pie dish. 
- Line the pie dish with the dough if you prefer a bottom crust. 
- In a large skillet, melt some butter and sauté onions, carrots, and celery until tender. 
- Add peas, thyme, and chicken. Mix well. 
- Sprinkle in flour, stirring constantly for one minute. 
- Pour in the chicken stock and cream, stirring until the mixture thickens. 
- Add salt and pepper to taste. 
- Transfer the filling into the pie dish. 
- Roll out remaining dough and place over filling. 
- Cut slits to allow steam to escape. 
- Bake in the preheated oven for 35-40 minutes or until the crust is golden brown. 
- Let it cool for 10 minutes before serving.