Add diced potatoes to a large bowl filled with cold water. Set aside.
Bring 2 quarts of water to a boil. Add chicken, reduce heat to a simmer and allow to poach; about 8 to 10 minutes. Remove the chicken to a plate to cool. Continue to simmer the broth, adding the bouillon until reduced by half, about 10 more minutes. Dice the chicken when cooled.
In a large skillet, heat the oil over medium-high heat. Add the onions and the celery cooking until translucent, 2 minutes. Stir in the flour and whisk until it forms a roux. Add the Italian seasoning and pepper; cook for 3 more minutes.
Whisk the roux into the broth and bring back up to a boil. Drain the potatoes. Add the potatoes and the chicken to the broth over low heat. Stir in the frozen vegetables. Place a lid on top and simmer until the potatoes are tender, about 15 minutes. Stir in cream and a pinch of sea salt and cook for 5 more minutes.
Preheat the oven as directed on the pie crust package.
Lay the pie crust on a baking sheet and place into the oven. Cook according to package instructions, or until the pie crust is golden brown. When the crust has cooled, break up into pieces.
Ladle the soup into bowls and garnish with the pie crust.