Bring a medium pot of salted water to a boil. Add the barley and cook to just shy of tender, 25 to 30 minutes. Drain in a sieve and run under cold water, then drain again.
Put the dried porcini mushrooms in a small saucepan with about 2 cups water. Bring to a low boil, then simmer until tender. Transfer the mushrooms with a slotted spoon to a food processor. Pour in all but the last few spoonfuls of the cooking liquid (grit from the mushrooms may settle there). Puree until smooth.
Heat the EVOO in a large Dutch oven over medium-high heat. Add the portobello mushrooms and cook until browned. Add the thyme, shallots, celery and carrots and season with salt and pepper. Cook until the vegetables are tender, 5 to 6 minutes. Deglaze with the sherry, stirring and scraping up any browned bits from the bottom of the pot with a wooden spoon. Stir in the stock, porcini puree and Roasted Garlic Paste.
Meanwhile, bring the steak to room temperature and sprinkle with salt and pepper. Heat a large nonstick skillet over medium-high heat. Drizzle the steak with EVOO, then cook for 7 to 8 minutes, turning once. Let rest on a cutting board for 10 minutes, then thinly slice and cut into bite-size pieces. Dress with the Worcestershire sauce.
Stir the parsley and barley into the soup, then ladle into shallow bowls. Arrange the steak on top of the soup.
Cook's Notes: The cooked barley can be refrigerated in a resealable plastic bag until ready to serve the soup. The soup, without the barley and steak, can be refrigerated for a make-ahead meal. Reheat over medium heat.
Preheat the oven to 425 degrees F. Arrange the garlic in a cluster on a large piece of foil and drizzle with 1/4 cup EVOO. Wrap up the garlic in the foil to make a tightly sealed pouch. Roast until very tender, about 45 minutes. Let cool, then squeeze the garlic from the skins into a food processor. Add the remaining 3/4 cup EVOO and the honey and season with salt and pepper. Puree until smooth, then transfer to a small container. (Alternatively, you can mash the garlic paste with a fork instead of using a food processor.)