Onions, Oh Cry!

May you grow like an onion, with your head in the ground!
(Vahksin zuls du vi a tsibeleh, mitten kup in drerd.)
-Yiddish Curse
Onions. To my grandmother they were part of her favorite curse (see above). To me, they are used in every stock I make and when you cook them down and let them soften and brown, caramelized onions are the most delicious thing.
This recipe comes from my favorite food blogger Lottie + Doof out of Chicago. The first time I made this soup I halved the recipe. But I liked it so much that I wish I hadn't...
Note: For most soups all I use is my Dutch Oven and an immersion blender. It makes cleaning up a cinch!
A Puree of Onions (Soup) with Butter Croutons and Grated Lemon Peel (Courtesy of Lottie + Doof, Adapted from Bon Appetit) 
12 tablespoons (1 1/2 sticks) butter, divided** (See "optional" note below. I used 8 tbls.)
24 cups thinly sliced onions (about 5 3/4 pounds) 
8 cups (or more) low-salt chicken broth (preferably homemade) 
1 1/2 cups 1/2-inch pieces torn crustless country-style bread 
16 fresh sage leaves (only if you want to add as a garnish-- really for special occasions) 
1 1/2 tablespoons (I used more) Sherry wine vinegar 
2 teaspoons finely grated lemon peel

    Melt 6 tablespoons butter in heavy extra-large pot over medium-high heat. Add onions; sprinkle with salt and pepper and sautรฉ until onions begin to soften, 15 to 18 minutes. Reduce heat to medium and sautรฉ until onions are very tender and deep golden brown, stirring often and adjusting heat as needed, 25 to 30 minutes longer. Remove 1 1/2 cups of caramelized onions and reserve for garnish.
    Add 8 cups broth to remaining onions in pot and bring to boil. Reduce heat and simmer 25 minutes to blend flavors. Cool slightly. Working in batches, puree soup in blender until smooth. Or use an immersion blender and puree to perfection!
    Season soup to taste with salt and pepper and 1 1/2 Tbl of Sherry Vinegar.
    Melt 2 tablespoons butter in medium nonstick skillet over medium heat. Add torn bread pieces and sautรฉ until bread pieces are crisp and golden, 5 to 6 minutes. Remove from heat and reserve.
    Serve soup with croutons, carmalized onions, and a splash of sherry vinegar, salt, pepper and some lemon zest. I added a few very thinly sliced (using a peeler) bits of Gruyere because I had some in the fridge.
    OPTIONAL** Cook remaining 4 tablespoons butter in small saucepan over medium heat until golden brown, stirring occasionally, 3 to 4 minutes. Add sage leaves and cook until slightly crisp, 30 seconds to 1 minute. Transfer leaves to small plate; reserve brown butter in saucepan. You can then add sage leaves to soup and drizzle with brown butter sauce. I didn't make the crispy sage and it was still delicious. It's another step that you don't really need but you can add for a special occasion!
    Bon Appetite!