Cook pasta of choice prior to starting per package directions.
Melt butter and olive oil over medium heat on stove top.
Add chopped onions and cook 3-4 minutes to translucent.
Stir in thyme and garlic. Then added sliced mushrooms.
Saute mushroom mixture approximately 7-8 minutes and then remove mushrooms from pan and set aside.
In separate bowl mix cornstarch with veggie broth and add to the pan along with coconut aminos and optional white wine.
Simmer about 1-2 minutes until the sauce starts to thicken stirring several times.
Add mushrooms back into the pan and season with salt & pepper.
Stir in sour cream and mix till thoroughly combined.
Serve sauce over pre-cooked pasta.