Preheat oven to 350°F.
Using a 12-inch ovenproof skillet, over medium-high heat, add the olive oil.
Add the onion and sliced celery. Sauté until onion is translucent and the celery is tender, stirring continuously for about 5 to 7 minutes.
Lower the heat to medium-low. Add the fresh minced garlic to the onion and celery. Cook for about 1½ to 2 minutes. Be very careful to stir continuously and do not burn the garlic. Burning the garlic will make it taste bitter.
Transfer the cooked onion, celery, and garlic to a bowl or plate and set aside.
Return the skillet to the stovetop keeping the heat at medium-low and add the 2 tablespoons of butter.
Once the butter is melted, whisk in the 3 tablespoons of flour. Continue whisking until the flour has absorbed the butter, for about 30 seconds to 1 minute.
Keeping the heat at medium-low, slowly whisk in the chicken stock. Continue whisking until the stock and flour mixture are smooth. Add the heavy cream and continue whisking.
Allow the broth mixture to come to a low simmer and begin to thicken. This may take 3 to 5 minutes.
Once the broth mixture is thickened whisk in the kosher salt, black pepper, rosemary, and thyme leaves.
Once the seasoning is well incorporated, remove the skillet from the heat.
Return the onion, garlic, and celery to the broth mixture. Use a large wooden spoon to stir the mixture.
Continue to stir and add the frozen peas, carrots, and chicken. Stir until it is entirely coated and evenly distributed. Leave the mixture in the skillet.
Open the two cans of biscuits. Cut each biscuit in half, then in half again.
Evenly top the chicken mixture with the biscuits.
Bake the skillet chicken pot pie for 30 minutes or until the biscuit tops are golden brown.
Melt the final tablespoon of butter. After removing the pan from the oven, using a pastry brush, evenly coat the tops of the biscuits.
Serve while hot.