Preheat oven to 375°.
In the liner of an electric pressure cooker, place all the ingredients for the filling EXCEPT the milk and flour. Cover and seal the cooker.
Cook using the pressure cook or manual setting on high for 12 minutes. When done, release the pressure.
Gently remove the chicken and place on a cutting board. Cut the chicken into bite size pieces or using two forks shred the chicken. Your choice.
Turn on the saute function of the pressure cooker. Bring the remaining contents of the pressure cooker to a boil.
Stir in the flour until thoroughly mixed and then cook until the sauce starts to thicken. Add the milk and chopped/shredded chicken. Stir carefully to combine.
Let the ingredients boil, but stir often to avoid scorching, for about 5 minutes or until the sauce has thickened and is able to coat the back of a spoon.
Transfer the chicken filling to a prepared casserole dish.
To prepare the biscuit topping, add the flour, baking powder, and salt to a food processor. Using the pulse button combine the dry ingredients. Then, add the butter a slice at a time to the mixture, pulsing to mix. When all butter is added, continue pulsing until the mixture looks like coarse sand. Turn on food processor and add the buttermilk in a continuous flow. Continue to blend until a dough forms.
Divide the dough into 6 to 12 mounds and roll into balls. Pat into biscuit shapes and place evenly across the top of the casserole. NOTE: If you are using frozen biscuits, thaw them out in advance so that the dough is soft before adding to top of casserole. If using canned biscuits, this is where you would place them on top of the casserole similar to prepared
biscuit dough.
Bake for 30 to 35 minutes or until the biscuits have browned slightly and cooked through. If desired, brushing the tops of the biscuits with melted butter adds an additional richness to the dish.
Before serving, let the casserole rest for 5 to 10 minutes. This will allow the filling to thicken