Dry sauté mushrooms until golden brown. Season lightly with salt & pepper; set aside to cool.
In a large bowl, shred the cooked crab meat with a fork. Mix in cooked mushrooms, thyme, garlic, and beaten egg. Mix thoroughly.
Mix in bread crumbs until the mixture is a good consistency to form patties. It should be moist but not dripping.
Heat a large skillet and melt enough butter or cooking oil to coat the pan. Form crab mixture into golfball-sized patties with your hands and place them one-by-one into the hot skillet. Do not crowd them.
Allow crab cakes to brown before turning, about 5 minutes. Flip cakes and squash down gently with your spatula, being careful not to break them up.
Serve hot with cocktail or tartar sauce. They can also be refrigerated and re-heated.