Preheat the oven to 400 degree F. Grease a 5X9 baking dish and keep it aside.
Heat a skillet over a medium heat; add oil, onions, garlic and carrots. Cook till the onions turn translucent for 2-3 minutes.
Add in the ground chicken and break them up with wooden spoon and cook for 5 minutes
Sprinkle the flour and cook for a minute. Add the tomato paste, Worcestershire sauce, chicken broth, and the spices; oregano, thyme, salt and pepper. Let it simmer for 5-6 minutes until the sauce thickens.
Add the frozen peas along, stir and remove from the heat. Transfer them to the prepared baking dish and set aside.
Meanwhile, peel the potato skin and cut them into cubes. Boil the potatoes in salt water for 7-8 minutes until potatoes are cooked through. Mash the potatoes with a masher along with the butter, heavy cream, salt and pepper. Add some parsley leaves and mash them until smooth.
Spread the mashed potatoes over the chicken mixture evenly covering the baking dish.
Bake the Shepards pie for 20-25 minutes until the top layer is slightly golden. Allow the pie to cool for 10 minutes before serving.
Garnish the pie with parsley and serve while it is still warm.