Remove the bacon to a paper towel-lined plate to drain. Once cool, cut the bacon in smaller pieces.
Add the onions to the pan with the bacon drippings and cook on medium heat until tender and translucent.
Increase heat to medium-high and add a few large handfuls of greens at a time and stir constantly to allow each batch to wilt for a few moments. Keep doing this until all of the greens fit into the pot.
Continue to sauté 3 – 5 minutes, until bright green and wilted.
Season with a very generous pinch of kosher salt and a few grinds of freshly ground black pepper.
Add the chicken stock, sugar, red pepper flakes and stir until combined.
Bring to a boil, then immediately reduce heat to low.
Cover and simmer for 15-20 minutes.
Add bacon and serve.
Gr8 Do-Ahead Tip:
This can be made a few hours ahead of time or up to a day in advance which will really allow the flavors to deepen. Just keep in the refrigerator until ready to serve. Reheat over low to medium-low heat until warm.