Place a deep pan over high heat and allow to get very hot. Add the portobello and white mushrooms in batches so as to not crowd the pan. Sauté for about 3-4 minutes, until golden on all sides.
When ready, transfer to a bowl and then add another batch. Repeat this process until all of the mushrooms are ready. Season generously with salt and pepper and set aside until needed.
In the same pan, add some olive oil and the pearl onions. Lower the heat to medium and sauté for about 2-3 minutes, until nicely caramelized.
Add the garlic and sauté for 1 minute. Then add the sautéed mushrooms and tomato paste. Sauté for 1-2 minutes before adding the wine. Cook until the alcohol evaporates.
Add the cinnamon, all-spice, bay leaves, canned tomatoes, and vegetable stock. Lower the heat to medium-low, cover the pan, and simmer for 30-35 minutes until the mushrooms soften and the sauce thickens. Ten minutes before it is ready, add the orzo, mix, and cook for the remaining cooking time or until soft.
When ready, remove from the heat and season to taste. Add the fresh mint and thyme and serve.