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Slow Cooker Green Bean Casserole

A hands-off, flavor-packed upgrade to the classic holiday side dish, featuring a from-scratch creamy mushroom sauce and tender green beans, all cooked to perfection in your crockpot.
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Prep Time 20 minutes
Cook Time 6 hours
Total Time 6 hours 20 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: American, Holiday
Calories: 280

Ingredients
  

Casserole Base
  • 2 pounds fresh green beans washed, trimmed, and cut into 1.5-inch pieces
  • 1 tbsp olive oil
  • 1 medium yellow onion finely diced
  • 8 ounces cremini mushrooms thinly sliced
  • 3 cloves garlic minced
Cream Sauce
  • 4 tbsp unsalted butter
  • 0.25 cup all-purpose flour
  • 1 cup chicken broth or vegetable broth
  • 1 cup heavy cream or half-and-half
  • 1 cup whole milk
  • 1 tsp soy sauce
  • 0.5 tsp black pepper
  • 0.5 tsp kosher salt
Topping
  • 1 6 oz can French-fried onions
  • 0.5 cup Parmesan cheese shredded, optional
  • 2 tbsp fresh parsley chopped, for garnish

Equipment

  • 4-6 Quart Slow Cooker
  • Large skillet
  • Whisk
  • Measuring Cups/Spoons

Method
 

  1. Wash, trim, and cut the fresh green beans into 1.5-inch pieces. Set aside.
  2. Heat olive oil in a large skillet over medium heat. Sauté the diced onion for 4-5 minutes until translucent. Add sliced mushrooms and cook for 6-8 minutes until golden. Add minced garlic and cook for 1 more minute. Transfer this mixture to the slow cooker.
  3. In the same skillet, melt the 4 tbsp of butter. Whisk in the flour and cook for 1-2 minutes to form a light blonde roux.
  4. Gradually whisk in the chicken broth until smooth, then whisk in the heavy cream and milk. Bring to a simmer until thickened, about 3-5 minutes. Stir in soy sauce, pepper, and salt.
  5. Pour the finished cream sauce over the mushroom mixture in the slow cooker. Add the prepared green beans and stir until everything is evenly coated.
  6. Cover and cook on LOW for 5-6 hours or on HIGH for 3-4 hours, until green beans are tender.
  7. In the last 30 minutes of cooking, stir in half of the French-fried onions and the optional Parmesan cheese. Before serving, sprinkle the remaining fried onions and fresh parsley on top.

Notes

For a crisper bean, check at the lower end of the cooking time. Frozen green beans can be used without thawing; add 30-60 minutes to cooking time. The casserole can be assembled in the slow cooker insert the night before and refrigerated.