Preheat oven to 400 degrees.
Heat oil in a large skillet. Cook onions, carrots, and celery until soft (about 5 minutes), stirring frequently. Add chicken. Sprinkle ¼ cup cassava flour and stir to distribute and allow it to brown slightly (about 1-2 minutes).
Add broth and cook until sauce is thick and bubbling, stirring constantly.
Add thyme and salt to taste. Pour into 1-2 quart baking dish and set aside.
In medium bowl, whisk together cassava flour, baking soda, and salt.
Using two forks or a pastry blender, mix in lard or vegetable shortening until well distributed.
Add water and mix with a spoon until dough forms.
Roll dough out on floured surface and cut into six round biscuits (the dough will be wet, so this may be tricky – it’s OK if your biscuits look a little “rustic!”).
Place biscuits on top of filling.
Bake for 30-35 minutes, or until biscuits are golden brown.
