Preheat the oven to 350°F.
Add the olive oil to the Dutch oven and heat over medium heat. Thaw the frozen puff pastry to room temperature.
Saute the onions and garlic in the Dutch oven for about 5 minutes or until softened.
Whisk flour and milk together in a mixing bowl until smooth. Pour the milk mixture into the Dutch oven.
Add the condensed cream of chicken soup, potatoes, frozen mixed veggies, and seasonings. Simmer until the potatoes are cooked through.
Stir in the shredded chicken.
Remove the Dutch oven from the heat.
Unroll the puff pastry and trim it to fit inside the Dutch oven, using the lid as a guide.
Put the puff pastry on top of the creamy chicken filling, making sure the edges are sealed. Bake the chicken pot pie uncovered for 35 to 40 minutes or until the top is golden brown and the soup is bubbling around the edges.
Remove the Dutch oven chicken pot pie from the oven and allow it to cool for 5 minutes before serving. Enjoy!