Step 1

Prep the mustard greens and garlic. Trim the thick bottom stems from 1 1/2 pounds mustard greens and discard. Coarsely chop the greens with their thin stems attached (about 12 cups). Rinse in a colander but do not dry. Thinly slice 3 garlic cloves.

Step 2

Sauté the garlic and red pepper flakes. Heat 2 tablespoons olive oil in a large, wide, high-sided sauté pan over medium heat until shimmering. Add the garlic and 1/4 teaspoon red pepper flakes if desired. Cook, stirring, until fragrant, about 1 minute (do not let the garlic brown).

Step 3

Add the mustard greens and cook. Add the mustard greens a few handfuls at a time, stirring after each addition so that they start to wilt, until all of the greens are added. Stir in 1/2 teaspoon kosher salt and 1/4 teaspoon black pepper. Cover and cook, stirring occasionally, until the mustard greens are tender, 10 to 15 minutes. Remove from the heat, stir in 1 tablespoon balsamic vinegar, and serve.