In a large skillet, cook the shallot, garlic, and sesame oil over medium-high heat for about 5 minutes, until the shallot is soft. Add the bell pepper, vegetable broth, coconut milk, mushrooms, pineapple, curry paste and ginger.
Place the lemongrass stalks on a cutting board. Trim off any brown areas and the top 3-inches of the stalk. With a dull edge of your knife or a meat tenderizer, crush the lemongrass stalks to release the flavor. Add the lemongrass to the soup.
Cook the soup for about 15 minutes, until the mushrooms and bell pepper are tender. Remove the lemongrass. Add the lime juice. Season with salt and pepper. Serve hot.