Preheat the oven to 375 degrees.
In a large bowl, add the cassava flour, coconut flour, olive oil, salt and baking powder. Stir to combine until a loose dough forms (because it is a grain-free dough it will be wetter than regular doughs). Form a ball and wrap with plastic wrap. Refrigerate for 20 minutes while you prepare the filling.
Heat the Baker’s Skillet over medium heat with 2 tablespoons of olive oil. Add the shallot and garlic. Cook, stirring, until the shallots are just tender, about 2 minutes. Add the mushrooms, thyme, sage, salt and pepper. Continue to cook, stirring, until the mushrooms are slightly tender, about 3 minutes. Add the remaining 1 tablespoon of olive oil. Sprinkle the cassava flour into the mushroom mixture and stir until evenly coated. While stirring, slowly pour in the broth, scraping up any browned bits on the bottom of the skillet. Bring to a simmer. Add the chicken and kale. Stir to combine and cook, stirring, until the kale has just wilted, about 3 minutes. While stirring, slowly pour in the creamer and the lemon zest until well-combined. Remove from the heat.
On a sheet of parchment paper, sprinkle 1 tablespoon of cassava flour over the top. Place the dough on top and gently coat, reshaping the dough ball. Place a second sheet of parchment paper on top. Using your hands, spread the dough into an approximately 12 inch circle. Carefully remove the top piece of parchment. Gently flip the dough over the top of the mushroom filling. Slowly remove the remaining parchment paper from the dough. Using a knife, puncture an “X” shape in the center.
In a small bowl, whisk the egg and brush the top of the pie. Transfer pie to the oven and bake for 15 minutes. Serve and enjoy!