Preparation

• Heat 2 tablespoons butter or oil to a large Dutch oven or pot. Cook the mushrooms until they are brown. You might have to do this in batches. Use a slotted spoon to transfer mushrooms to a large bowl and sprinkle with salt and pepper.
  Add another 2 tablespoons butter and brown the onions, seasoning them as you go. Transfer to bowl with mushrooms.
  Reduce heat to medium-low. Add another tablespoon butter or oil to pan. Add sliced carrots and minced garlic cloves and sauté for 1 minute longer. Stir in tomato paste and flour and then add wine, broth, soy sauce, thyme and bay leaf, scraping up the brown bits at bottom of pot.
  Add reserved cooked mushrooms and pearl onions back to the pot and bring to a simmer. Partly cover the pot and simmer on low heat until carrots and onions are tender and sauce is thick, 20 to 30 minutes. Taste and add season if needed. Discard the bay leaf.
  Serve mushroom Bourguignon over polenta, topped with parsley.