Warm butter bean, red onion, and spinach salad with mustard recipe

Even after making Brunswick stew this week (which is getting better and better!), I still have butter beans in my freezer (for some reason I thought it was a great idea to cook 3 pounds of them a few months ago).  Before I made the stew, I was inspired by Gel's kitchen to make this salad.  I made the recipe and it was pretty good, but then I got the idea to add whole grain mustard.  Sometimes I have random last-minute ideas that fail miserably, but this one took the salad from ok to wonderful.  Next time I'll probably add more spinach, but it was great just as I made it.  I tried the leftovers warm and cold and couldn't decide which way was better.

Now the only problem is deciding how I want to use my last bag of butter beans.  Do I make more of this salad?  Do I try mashing them up like potatoes (an interesting idea I just read about)?  Any favorite recipes out there?

Warm butter bean, red onion, and spinach salad with mustard (adapted from Gel's kitchen)
(Printable version)

1 Tbsp olive oil
1/4 large red onion, sliced thinly
2 1/2 cups cooked butter beans
salt and pepper to taste
2 large handfuls spinach
2 Tbsp whole grain mustard (I used one with horseradish)

Heat oil in a large skillet over medium heat, and then saute the onion until it's very tender (about 10 min).  Add butter beans to the skillet, season with salt and pepper, and stir everything around for a couple of minutes.  Then add spinach, stir well, and cook until the spinach wilts.  Stir in the mustard and serve.  Serves 3-4.