Heat your 12" cast iron skillet (or largest oven safe skillet) over medium heat. Preheat your oven to 350°F.
Add the olive oil, celery, leeks, carrots and onion. Season with kosher salt and pepper. Cook, stirring occasionally until soft, about 10-15 minutes.
While the vegetables are getting soft, make the biscuit crumble topping. In a medium size bowl combine all the ingredients and stir to combine. The dough should be just a little tacky. If it seems too wet, add more almond flour until it's just a little tacky. Set aside.
To the softened vegetables, add the rosemary, thyme, dried sage, dried garlic and chopped chicken (or turkey). Stir to combine and cook another 3-5 minutes.
In your high speed blender (or food processor) add the squeezed out cauliflower rice pulp and the chicken stock. Blend on high speed until completely pureed.
Add the cauliflower puree into the skillet with the cooked vegetables and chicken. Stir to combine and warm through.
Add the heavy cream and parsley. Stir to combine. Taste for salt and pepper and add more to taste if needed.
Using 2 hands, crumble grape size pieces of the biscuit batter all over the top of the pot pie. It doesn't need to be perfect, the more rustic looking the better.
Bake at 350°F for 20-25 minutes until the biscuit crumble topping is golden brown. Remove from the oven and cool for 5 minutes.
Serve warm. Leftovers will keep in an airtight container refrigerated for at least 5 days, or frozen for at least 6 months.
See Notes below for more tips, tricks and substitution recommendations!