Remove tough stems from collard greens: stack leaves, fold, run a knife along the stem to remove, then stack and roll leaves and slice into 1/2-inch ribbons. Coarsely chop mixed greens if large. Rinse all greens thoroughly and spin or pat dry.

Dice the onion finely and mince the garlic. Measure out broth, vinegar, and seasonings.

Cook Aromatics

Warm the pan

Place a large wide skillet or sauté pan over medium heat. Add olive oil and butter and heat until butter melts and begins to foam, about 1 minute.

Add the diced onion and a pinch of salt. Cook, stirring occasionally, until the onion is translucent and beginning to brown at the edges, about 5–7 minutes.

Stir in the minced garlic and red pepper flakes and cook for 30–45 seconds until fragrant, taking care not to burn the garlic.

Wilt Greens & Simmer

Add the chopped collard greens to the pan. They will mound; use tongs to press them down so they contact the pan. Cook, stirring occasionally, until partially wilted, about 3–4 minutes.

Pour in 1 cup of broth, add the apple cider vinegar, and sprinkle in the sugar (if using). Stir to combine, then cover the pan with a tight-fitting lid or foil. Reduce heat to medium-low and simmer until collards are tender, about 12–15 minutes. Check once and stir so the greens cook evenly; add up to 1/4 cup additional broth if pan becomes dry.

After collards are tender, remove the lid and add the mixed greens. They will wilt quickly; cook, stirring, until just wilted and bright, about 1–2 minutes.

Finish & Taste

Season the mixture with kosher salt and freshly ground black pepper. Stir in the lemon juice if using and taste: adjust salt, pepper, or a touch more vinegar or sugar to balance bitterness.

If desired, sprinkle toasted nuts and grated cheese on top for texture and richness. Serve warm.