Prep the vegetables: trim and halve or quarter the cremini, cut the portobello into 2.5 cm chunks, slice the carrots, dice the onion, and mince the garlic. Thaw the pearl onions under running water for about 1 minute if they're frozen.

Heat 1 tbsp olive oil in a 5.5-quart / 5.2 L Dutch oven over medium-high heat until it shimmers. Add one third of the mushrooms in a single layer and leave them alone for 2 minutes, then stir now and then for 3 to 4 minutes more until deep brown. Move them to a 2-quart / 2 L bowl and repeat twice with the remaining oil and mushrooms. Crowding the pot makes them steam and turn gray, so keep to three batches.

Lower the heat to medium and melt the vegan butter in the same pot. Add the onion, carrots, and 1/2 tsp salt, and cook for 6 minutes until the onion is soft and golden at the edges. Stir in the garlic and tomato paste and cook for 2 minutes until the paste darkens to brick red. Sprinkle in the flour and stir for 1 minute.

Pour in the wine and scrape up the browned bits from the bottom of the pot. Simmer for 4 minutes until the wine has reduced by about half.

Add the broth, soy sauce, Dijon, thyme, bay leaves, pearl onions, and the browned mushrooms with any juices from the bowl. Bring to a boil, then lower the heat to a gentle simmer. Cook uncovered for 25 minutes, stirring now and then, until the carrots are fork-tender and the sauce coats the back of a spoon.

Fish out the bay leaves and thyme stems. Stir in the remaining 1/2 tsp salt and the pepper, then taste and adjust. Ladle into bowls and top with the chopped parsley.