Step 1

Trim leeks so that about 1 1/2 inches of green leaves remain, and slice the leeks in half lengthwise. Separate leaves and pull the leeks apart to rinse away any dirt and sand in the layers, then chop leeks into 1 1/2-inch pieces.

Step 2

Melt butter in a skillet over medium heat, and cook and stir the leeks until they begin to separate and soften, about 5 minutes. Stir in mustard greens, and pour in enough chicken broth to just cover the bottom of the pan and prevent leeks from browning. Cook the leeks and mustard greens until the greens turn bright green and start to soften, another 2 to 3 minutes. Season to taste with salt and black pepper, and sprinkle with Parmesan cheese.