1bunch collard greenswashed, trimmed, and sliced into 1-inch crosswise strips (my bunch weighed about 11 ounces)
1tablespoonred wine vinegar
Kosher salt and freshly ground black pepper
Heat the olive oil in a large saucepan over medium-high heat. Add the pancetta and cook for a few minutes until the fat begins to render and the meat starts to crisp. Add the onion and continue to cook until softened, a few more minutes.
Add the garlic and chili flakes and cook for another minute, being careful not to burn the garlic (lower the heat a bit if necessary). Deglaze the pan with a splash or two of the broth, scrapping the bottom to make sure any browned up bits of pancetta and onion are released.
Add the greens to the pot along with the remaining chicken broth, red wine vinegar, and sugar, stirring to make sure everything is well-coated. The greens will begin to wilt. Season with salt and pepper (you can season more throughout the cooking process as needed–be careful not to oversalt, as the greens can get salty as the mixture reduces).
When the liquid comes to a boil, lower the heat to maintain a simmer and cover the pot. Continue to cook, covered, for about 1 hour and 20 minutes, or until the greens are tender (test the center stalky part). Adjust seasoning as needed. Serve hot.