Bring a large pot of water to boil. Once water is boiling, place green beans in pot and cook for 2 minutes. Strain green beans and set aside.
Stir together flour and bread crumbs. Toss onions in breading and fry in vegetable oil over medium-high heat until golden brown. Discard oil.
Saute baby bella mushrooms in butter with garlic and nutmeg. Add balsamic vinegar, vegetable broth, salt, and pepper and bring to boil. Add half and half and cook on medium high for 3 minutes to reduce.
Mix in green beans and sliced almonds.
Transfer to baking dish and top with fried onions, thyme, and additional salt and pepper. Bake for 20 minutes.
Recipe by Rachel Schultz at https://rachelschultz.com/2017/11/06/a-not-gross-green-bean-casserole/