In large saucepan over medium, heat olive oil. Add onions and sauté for 5 minutes. Add in garlic and sherry and cook for a minute. Add stock and potatoes. Bring to a boil and cook for 15 minutes. Then add peas and continue to cook until potatoes are fork-tender, approximately another 15 minutes.

With an emersion blender, or transferring to a blender, purée soup until smooth. Add truffle oil and stir to combine. Season with salt and pepper, if using. Optionally, serve with extra truffle oil drizzled overtop, but remember: a little goes a long way.