Before assembling everything make sure the vegetables are chopped, the chicken is shredded and measure out the seasonings, herbs and other ingredients so you don't miss anything.
Place a large cast iron skillet over medium high heat. After a minute or two turn the heat to medium and add 2 tablespoons butter.
Once the butter has melted toss in the chopped onion, carrot, celery and potato. Season with 1/2 teaspoon sea salt and ground pepper. Stir to combine and cook 5-7 minutes until the veggies are softened and slightly browned. Add the minced garlic and saute another minute till fragrant.
Now make the sauce. Sprinkle the flour over the vegetables, stir until combine and cook a minute or two until deeply browned. Continue stirring and slowly pour the bone broth. Make sure to scrape the bits up on the bottom of the pan. Still stirring, slowly pour in the milk. Once combine, add in the dried rosemary, thyme and sage. Bring to a simmer and cook about 5-7 minutes until thickened. Don't stop stirring. Taste and season with more sea salt and ground pepper to taste.
Remove the sauce from the stove and mix in the shredded rotisserie chicken and frozen green beans. Then remove the biscuits from the refrigerator and place 8 of them neatly on top of the sauce.
Crack an egg into a bowl and beat lightly with a fork. With a pastry brush, brush the whisked egg onto the tops of each biscuit. Transfer the warm skillet to the hot oven and bake the pot pie 20-25 minutes until the biscuits are golden and cooked through.
Carefully remove the deconstructed pie from the oven, cool slightly and serve with sea salt flakes, a drizzle of honey and red pepper flakes if desired.
Store leftover in an airtight container in the refrigerator for up to 6 days.