Preheat the oven to 375ºF.
Melt butter in a Dutch oven over medium heat; add mushrooms, red pepper, onion, and celery. Season with salt and pepper. Cook for 5 minutes.
Add garlic and sage; cook for 1 minute. Add broth, whipping cream, bay leaves, and glucomannan (if using). Bring to a simmer.
Season with salt and pepper; add chicken and cook for 10 minutes until done. Remove bay leaves.
Transfer filling to a baking dish, leaving half the cooking liquid behind.
Biscuit Topping:
In a bowl, whisk almond flour, coconut flour, baking powder, garlic powder, and salt. Stir in half the cheese.
Add eggs, sour cream, and melted butter; mix well and let sit. Drop spoonfuls of topping over filling, sprinkle with remaining cheese, and bake for 20-25 minutes. Let stand 10 minutes before serving.