In a large bowl or container, combine the pearl onions, carrots, bay leaves, thyme, 1 cup red wine, and 2 cups vegan beef broth. Cover and refrigerate for at least 10 hours or overnight.

Place dried porcini mushrooms in a bowl and cover with 1 cup hot water. Let soak for 20 minutes. Once softened, finely chop the mushrooms and reserve the soaking liquid.

Preheat oven to 350°F (180°C).

Drain the marinated vegetables, reserving the liquid. Set aside the bay leaves and thyme for reuse.

Heat 1 tablespoon vegan butter or a drizzle of olive oil in a Dutch oven over high heat. Add the pearl onions and sauté until golden-brown in spots. Remove and set aside.

Add a little more oil if needed, then sauté the brown and white mushrooms until browned and all moisture has evaporated. Set aside with the onions.

Lower heat to medium and add the remaining 2 tablespoons vegan butter to the pot. Add the carrots, reserved bay leaves, and thyme. Sauté for 2–3 minutes, then add the red bell pepper and cook for 2 more minutes.

Stir in the garlic and cook for 1 minute.

Return the sautéed onions and mushrooms to the pot along with the chopped porcini.

Stir in tomato paste and cook for 1 minute to coat the vegetables. Sprinkle in the flour and stir well until a paste forms.

Gradually add 1 cup vegan beef broth, stirring constantly to avoid lumps. Then stir in the reserved marinade, porcini soaking liquid, 1 cup red wine, and soy sauce.

Bring to a boil, then reduce heat and simmer uncovered for 20 minutes, stirring occasionally.

Cover the Dutch oven and transfer it to the oven. Bake for 1 hour at 350°F (180°C) until the sauce has thickened and the vegetables are tender.

Serve hot over mashed potatoes and garnish with fresh thyme, if using.