In a small pot, saute the mushrooms for several minutes, stirring frequently, until they are reduced in volume and all the excess water is evaporated. If your mushrooms stick, add a splash of water to the pan.
Meanwhile, add the tapioca flour to the cup of water and stir well. Set aside.
Add the garlic to the mushrooms and saute for 30 seconds.
Add the thyme and salt and pepper, to taste.
Give the tapioca flour/water mixture a stir and slowly add it to the mushrooms. Stir until the gravy has thickened. If you prefer a thinner gravy, add a little more water and stir.
This gravy can be made in advance and reheated. It will last for up to 3 days refrigerated.To freeze the gravy, let it cool to room temperature, place it in a glass container leaving a little space at the top, then add the lid and place it in the freezer. Don’t forget to let the frozen gravy thaw in the refrigerator before reheating it in a saucepan.