Combine the fennel, leek, bay leaf, vegetable bouillon, and water in a pressure cooker. Lock the lid of the pressure cooker, bring it up to pressure, reduce heat to maintain pressure, and cook for 15 minutes. Remove cooker from the heat and let the pressure reduce on its own, 5 to 10 minutes. If your pressure cooker does not have a quick-release function, reduce cooking time slightly as food will continue to cook while pressure releases slowly.
Stir the olive oil into the soup, and sprinkle with Parmesan cheese to serve.