Remove tough stems from greens and slice leaves into ribbons. Rinse thoroughly and set aside.
In a wide pot or Dutch oven over medium heat, add onions and mushrooms with a splash of broth. Cook 8–10 minutes, stirring often, until the mushrooms release their moisture and become deeply browned and almost jammy.
Bloom the smoke by adding garlic and smoked paprika. Stir constantly for 30 seconds until fragrant.
Add greens, bay leaf, liquid smoke, remaining broth, and a pinch of salt. The greens will look like too much — they’ll cook down. Cover and reduce heat to low.
Braise gently for 30–40 minutes, stirring occasionally, until greens are tender, silky, and deeply flavored. Add a splash of broth if needed.
Remove bay leaf. Stir in apple cider vinegar, maple syrup (if using), black pepper, and red pepper flakes if desired. Taste and adjust salt.