*If you've never tried shallots, they're great! They're small onions that practically melt into the food. If your store doesn't carry shallots, yellow onions will also work, but the flavor will be a little different.
** If you can't find mascarpone cheese, cream cheese or creme fraiche can be substituted. Sour cream may even work, but the soup won't be as sweet. You can even make your own: follow these instructions: http://www.blogher.com/how-make-mascarpone-cheese-only-3-ingredients
Adapted from Epicurious