Heat oven at 350 degrees. On a large baking sheet, place Butternut Squash on one side and Bread slices on other side. Drizzle both with a little Olive Oil, flipping, if needed. Bake on middle rack for 10 minutes and then carefully flip bread onto it's other side to brown for an additional 10 more minutes. Then remove bread from tray/oven and place on a plate and set to the side. Spread the squash out on the tray and place back into the oven for another 10 more minutes or until soft.
While that is cooking, in a large pot, on a medium flame, heat oil and then toss in both sets of onions, mushrooms, garlic, and bay leaf. Saute them for about 15 - 20 minutes, scraping the bottom of pot for brown pieces. If it's cooking to fast then turn the heat to low. When your squash is done cooking, remove from oven and add directly into pot along with your vegetable broth, worcestershire sauce, and Sea Salt and Pepper and let simmer for 5 - 10 minutes. (I did find that I need a little more salt in this soup to compensate for the natural sweetness from the squash and onions.) Remove Bay Leaf.
Heat the broiler in your oven, and place your bread slices on that same baking sheet and liberally sprinkle your cheese on top of them. Top them when a couple of sage leaves and a drop of olive oil and broil them for a couple of minutes or just until golden brown and remove from the oven once done.
Place your beautiful sage crostini's on top of your soup and then enjoy!