Slow Cooker Green Bean Casserole

Ingredients

• Butter — Both unsalted or salted butter work here.
• Baby Bella or cremini mushrooms — Purchase these mushrooms pre-sliced if you can find them that way. One less thing to do!
• Garlic — I used the minced garlic in the jar but you can mince your own. Any name brand is fine. 
• Flour — All-purpose white flour works best when making the roux for the mushroom sauce in this green bean casserole. 
• Milk — Whatever milk you have in your fridge is just fine in this recipe. 
• Heavy cream — Don’t skimp on the real heavy cream. Substituting extra milk will not be creamy enough. If your grocery is out of heavy cream you can use half and half. 
• Parmesan cheese — I purchase pre-shredded parmesan. Any kind will do. But if you want it to be extra creamy, grate parmesan from fresh. 
• Fresh green beans — For simplicity, I use two 12 oz packs of green beans. But if you can’t find those, you can use 24 oz of fresh green beans and trim the ends. 
• French fried onions — Hurry and go now to find the French fried onions. I’m always afraid these will be out of stock before Thanksgiving and stock up. Any brand is yummy.

Here’s How You Make It

1. First, start the mushroom sauce by melting 1 tablespoon of the butter over a medium-high heat in a high-sided frying pan or a large saucepan. Once the butter is frothy, add the mushrooms and a pinch of salt, and cook until the mushrooms are soft and start to color. (photo 1)
2. Next, add the minced garlic and stir, cooking for a few minutes more until the garlic starts to become aromatic. Then, season the mushrooms with black pepper, remove them from the pan, and set them aside. (not pictured)
3. Now make the roux by melting the remaining 4 tablespoons of butter in the pan. To the butter, add the flour and whisk them together for a few minutes to remove the ‘raw’ taste from the flour. (not pictured)
4. To the roux, gradually pour in the milk, whisking the whole time, until you have a smooth sauce. Keep cooking and whisking the sauce often, until it is thick enough to coat the back of a spoon. (photo 2)
5. Take the sauce off the heat before stirring in the heavy cream, nutmeg, and shredded parmesan. Whisk this mixture again until it’s smooth. Add back the cooked mushrooms and season to taste with more salt and pepper, if needed. (photos 3-4)
6. Cut the green beans in half so they fit in the slow cooker better and transfer them to the cooking insert. Stir in the mushroom sauce. (photo 5)
7. Put the lid on the slow cooker green bean casserole and set to cook on low for 4 hours, or until the beans are tender but still retain a little bit of their crunch. (Depending on the size and shape of your slow cooker, you may need to stir occasionally during cooking to make sure the beans cook evenly.) (not pictured)
8. Finally, top the casserole with the French onions just before serving. (photo 6)

Expert Tips and Tricks

• This recipe halves perfectly for smaller slow cookers.
• Want to free up that stove space even more? If you have a sear-and-stew model of slow cooker or use the slow cooker setting of an Instant Pot, the mushrooms can be cooked and the sauce can be made in the cooking insert.