Combine the chicken, stock, potatoes, onions, carrots and seasoning in the Instant Pot and pressure cook on high for 4 minutes.
Natural release for 5 minutes, then use the quick release to release the remaining pressure.
Heat the butter and flour for the roux in a cast iron skillet over medium heat.
Cook for about 3-5 minutes, whisking constantly. Remove from heat and set aside.
Turn the Instant Pot to the sauté setting (low if your Instant Pot allows it).
Heat the roux over medium heat and SLOWLY whisk in the milk, whisking constantly until a paste forms.
Stir the paste into the chicken mixture and bring to a simmer until thickened slightly.
Pour the mixture into an ovenproof baking dish.
Place the puff pastry sheet over top of the baking dish and seal around the edges. Cut 3 slits in the top.
Bake for 12-18 minutes, until the puff pastry is golden brown.
Serve hot.
Notes
Make sure your chicken is cut into 1-inch pieces. If the pieces are larger, the chicken will take longer to cook and the veggies may get too soft.
Don’t chop your potato into really small pieces as it will just get mushy.
When making the roux, make sure you stir it constantly so it doesn’t burn and slowly whisk in the milk.
Wait for the filling to pressure cook before adding the roux mixture. If you pressure cook it with the filling, it may burn and could prevent pressure from building in the Instant Pot.
Once you have the puff pastry arranged on top of the pie, make sure you put a few slits in the topso the pie can breathe.
Instead of one large pie, you can make a few mini or individual sized pies.
When releasing the pressure, make sure you naturally release it for 5 minutes. The filling keeps cooking during this time.
While the cooking time for the filling is just 4 minutes in the Instant Pot, you’ll also need to factor in time for pressure to build and release.