Bring a large pot of salted water to a boil (should taste like the ocean!)
Meanwhile, in a large saute pan, warm olive oil over medium high heat
Add sliced mushrooms and saute until tender (about 4 minutes)
Once water is up to a boil, drop green beans in and keep at a rolling boil
Get a large bowl of ice water ready to shock the green beans once they are finished cooking
Once green beans are tender, but still a slight crunch and bright green, drain water and dump into ice water. This keeps the green beans from overcooking.
In a food processor, process the ½ cup olive oil, pecan pieces, red wine vinegar, dijon, salt and pepper until combined. Make sure not to over process because you still want the nuts to be chunky and not pureed.
Once the green beans are cooled, drain from ice water and toss with the mushrooms and pecan dressing.
Place into casserole dish and bake at 350 degrees for 20 minutes (or until warmed through).