In a bowl, place the crimini mushrooms and the reconstituted dry mushrooms, if using. Add the sage, 1 tsp thyme, salt and ground black pepper to taste and the flour. Mix well to coat the mushrooms. It's okay if you have some dry flour remaining at the bottom of the bowl, it will form a nice roux to thicken the stew.
Heat 1 tbsp oil in a saucepan large enough to cook the stew in. Add the mushrooms along with any remaining flour and cook, stirring frequently, over medium-high heat until the mushrooms brown. Scrape the bottom of the pan if the flour sticks. The mushrooms should express enough moisture for you to do this easily enough, but it's okay if some brown bits remain stuck, they will add more flavor to the stew. Remove the mushrooms to a plate and set aside.
Heat the remaining oil in the same pan. Add the onions, celery and carrots. Season with salt and ground black pepper and saute until the onions turn translucent and the veggies are somewhat softened.
Add the remaining thyme and garlic and saute another two minutes. Add the wine or brandy and let the alcohol cook off. When most of the moisture has evaporated, add the tomato paste and mix well.
Add the vegetable stock (or the reserved mushroom stock) and the tamari. Stir well to mix. Add the reserved mushrooms.
Bring the stew to a boil. Add more water or vegetable stock if it seems too thick. Just before you turn off the heat, check for seasoning and add more salt and ground black pepper if needed. Add the vegan butter and stir it in.
Serve hot over a bed of noodles or mashed potatoes.