3 medium red onions, chopped coarse (about 3 cups)
1 1/4 cups chicken broth
1/4 cup cider vinegar
2 tablespoons firmly packed dark brown sugar, or to taste
1/2 teaspoon dried hot red pepper flakes, or to taste
4 pounds collard greens (preferably small leaves), coarse stems
and ribs discarded and leaves and thin stems washed well,
drained, and chopped coarse
In a deep heavy kettle cook bacon in 2 batches over moderate heat
until crisp and transfer to paper towels to drain. Pour off all but
about 3 tablespoons drippings and in drippings remaining in kettle
cook onions, stirring occasionally, until browned slightly and
softened. Transfer onions with a slotted spoon to a bowl.
To kettle add broth, vinegar, brown sugar, red pepper flakes, and
about half of bacon, stirring until sugar is dissolved. Add about
half of collards, tossing until wilted slightly, and add remaining
collards, tossing until combined. Simmer collards, covered, 30
minutes. Stir in onions and simmer, covered, 30 minutes more, or
until collards are very tender.
Serve collards topped with remaining bacon.