In a large mixing bowl, combine all-purpose flour, granulated sugar, baking powder, baking soda, and fine sea salt. Using a pastry cutter, cut cold unsalted butter into the dry ingredients until the mixture resembles coarse crumbs. Stir in buttermilk until just combined. Shape the dough into a rectangle, fold it over itself several times, wrap in plastic wrap, and refrigerate for 30 minutes to chill.

While the dough chills, bring a pot of salted water to a boil. Add quartered mini Yukon potatoes and cook until tender, about 10-15 minutes. Once cooked, drain the potatoes and set them aside, allowing them to cool slightly as you prepare the filling.

Heat a large skillet over medium heat and add a tablespoon of olive oil along with a tablespoon of unsalted butter. Once the butter has melted, toss in diced yellow onion, carrots, celery, and minced garlic. Sauté the vegetables for about 5-7 minutes until they are tender and fragrant.

Sprinkle all-purpose flour over the sautéed vegetables to form a roux, stirring constantly for about 1-2 minutes. Gradually whisk in chicken stock and heavy cream, bringing the mixture to a gentle simmer. Cook for 3-5 minutes, or until the sauce thickens and coats the back of a spoon.

Remove the skillet from heat, and fold in the cooked chicken or turkey, tender potatoes, frozen peas, and chopped fresh parsley into the creamy sauce. Transfer this hearty filling into a large baking dish or an oven-safe skillet.

Preheat your oven to 425°F (220°C). Remove the chilled biscuit dough from the refrigerator and turn it out onto a floured surface. Pat it to about 1-inch thickness, then cut into circles using a biscuit cutter. Place the biscuit rounds evenly over the pot pie filling and bake for 12-15 minutes, or until golden brown.