I found it on Pinterest, but the orginal recipe is found on a site called Kalyn's Kitchen. The link is here: http://www.kalynskitchen.com/2009/01/recipe-for-roasted-green-beans-with.html
Roasted Green Beans with Mushrooms, Balsamic, and Parmesan
(Makes 4-6 servings, recipe created by Kalyn, and copied here for reference)
8 oz. mushrooms, sliced in 1/2 inch slices (I used brown crimini mushrooms, but any mushrooms will work)
1 lb. fresh green beans, preferably thin French style beans
1 1/2 T olive oil
1 T balsamic vinegar
salt and fresh ground black pepper to taste
2 T finely grated parmesan cheese
Preheat oven to 450F/230C. Wash mushrooms and let drain (or spin dry in salad spinner, which is what I did.) While mushrooms are drying, trim ends of beans and cut beans in half so you have bite-sized pieces. (An easy way to trim them is to gather a small handful of beans, stand them up on cutting board, holding loosely so they will fall down and have ends ends aligned, then trim. Repeat with other end.) Cut mushrooms into slices 1/2 inch thick.
Put cut beans and mushrooms into a Ziploc bag or plastic bowl. Whisk together olive oil and balsamic vinegar and pour over, then squeeze bag or stir so all the beans and mushrooms are lightly coated with the mixture. Arrange on large cookie sheet, spreading them out well so beans and mushrooms are not crowded. Roast 20-30 minutes, starting to check for doneness after 20 minutes. Cook until beans are tender-crisp, mushrooms are cooked, and all liquid on the pan from mushrooms has evaporated. Season beans to taste with salt and fresh ground pepper, then sprinkle with finely grated Parmesan. Serve hot.
A few things I learned about this recipe -
Make your mushroom pieces a good size. They will burn if they overcook. The beans will just shrivel and become tasteless (yes, unfortunately I learned this the hard way). About a third of the veggies I cooked came out over done. Consistent sizing is also very important!
Ensure that your veggies are thoroughly coated before putting them in the oven. I think mine were a little dry and I ended up having to coat them with a little balsamic glaze when they came out of the over.
Other than that, this recipe was a big success! My family does not like green beans, so seeing an entire pound of them get demolished was pretty heartwarming.