I would like to post some recipes for you, but I'm sensitive to copyright laws. Instead I'm giving you some links to web pages that have lots of archived recipes you can search by ingredient. I chose the following with an eye for their variations on mustard greens and garlic (since we have more of these than we know what to do with) and for easy recipes with short preparation times.
Includes such recipes as "Sauteed mustard greens with garlic" and "Wilted mustard green pasta"
Look out for "Chili-Garlic Mustard Greens"
Not a huge selection, but they did have a nice once called "Spicy Mustard Greens with Asian Noodles"