Chicken pot pie with milk poached chicken

Name: Chicken pot pie with milk poached chicken
Cuisine: American
Ingredients: 4 cups of Clover Sonoma Non-GMO Lactose Free Milk (Whole or 2%); 1 large onion, diced; 3 cloves of garlic, minced; 1 pound of boneless chicken breasts or thighs; a few sprigs of fresh oregano; 4 cups of chicken stock; 2 large white potatoes, peeled and diced; 4 carrots, peeled and diced; 1 cup of frozen peas; 1 tablespoon olive oil; Salt and pepper; 3 tablespoons cornstarch; 1 package puff pastry, phyllo dough or pie dough