A homemade Thanksgiving classic loaded with crispy bacon, sautéed mushrooms, fresh herbs, and a rich Parmesan cream sauce, all topped with golden, crispy fried onions!

Green bean casserole might not usually be the most exciting dish on the Thanksgiving table, but this Bacon & Parmesan Green Bean Casserole is here to change that. We're skipping the canned cream-of-mushroom soup and making our own creamy, savory sauce with sweet onions, sautéed mushrooms, fresh sage, rosemary, half-and-half, and plenty of Parmesan. And because everything is better with bacon, we're adding an entire pound of it.

The green beans get tossed in that rich, homemade mushroom sauce along with all the crispy bacon, then baked until hot and bubbly. Of course, we're still finishing everything with a generous layer of crispy fried onions, because that's one Thanksgiving tradition I'm not willing to mess with. It's cozy, comforting, a little indulgent, and exactly the kind of side dish that deserves a spot on your Girlsgiving table!

Here are the Ingredients for this Bacon Parmesan Green Bean Casserole:

Produce: Fresh Green Beans, Sweet Onion, Cremini Mushrooms, Garlic, Fresh Sage, Fresh Rosemary
Meat: Bacon
Dairy: Unsalted Butter, Half-and-Half, Parmesan Cheese
Broth & Stock: Chicken Broth
Baking & Pantry: All-Purpose Flour, Crispy Fried Onions
Spices & Seasonings: Kosher Salt, Freshly Cracked Black Pepper

More Thanksgiving Side Dishes You’ll Love!

Yield 10-12

Author Casey Cheek

Prep time

25 Min

Cook time

45 Min

Total time

1 H & 10 M

Bacon Parmesan Green Bean Casserole

A homemade take on the classic Thanksgiving green bean casserole, made with fresh green beans, crispy bacon, sautéed mushrooms, sweet onions, fresh sage and rosemary, and a rich Parmesan cream sauce. Finished with a golden layer of crispy fried onions!

Ingredients

3 lbs hericot vert green beans, trimmed and sliced in half
1 lb bacon, chopped
4 tbsp unsalted butter (½ stick)
Half of the rendered bacon grease, reserved
1 large sweet onion, diced
1 cup cremini mushrooms, sliced
1-1 1/2 cups shitake mushrooms, sliced
4 garlic cloves, minced
1 tbsp fresh sage, finely chopped
1 tsp fresh rosemary, finely chopped
1 tbsp fresh thyme, finely chopped
½ cup all-purpose flour
1½ cups chicken broth
1½ - 2 cups half-and-half
¾ cup freshly grated Parmesan cheese
1 tsp freshly cracked black pepper
1 tsp salt
2–2½ cups crispy fried onions
Additional Parmesan cheese, optional
Reserved crispy bacon, optional

Instructions

Bring a large pot of generously salted water to a boil. Add the trimmed green beans and cook for 4–5 minutes, until bright green and just tender but still slightly crisp. Transfer immediately to an ice bath to stop the cooking. Drain thoroughly and pat dry to remove excess moisture.
In a large, deep skillet over medium heat, cook the chopped bacon until golden brown and crispy. Using a slotted spoon, transfer the bacon to a paper towel-lined plate. Pour off approximately half the rendered bacon grease, leaving the remaining grease in the skillet.
Add the butter to the reserved bacon grease. Once melted, add the diced sweet onion and cook for 5–7 minutes, until softened and translucent. Add the sliced mushrooms and continue cooking for another 7–10 minutes, until golden brown and most of their moisture has evaporated.
Stir in the minced garlic, fresh sage, thyme and rosemary. Cook for another 1–2 minutes until fragrant.
Sprinkle the flour evenly over the mushroom mixture, stirring constantly until the vegetables are coated. Cook for 2 minutes to eliminate the raw flour taste.
Gradually pour in the chicken broth, stirring constantly to incorporate the flour. Slowly add the half-and-half, continuing to stir until smooth. Bring to a gentle simmer and cook for 5–8 minutes, stirring frequently, until the sauce becomes thick and creamy.
Reduce the heat to low and stir in the grated Parmesan until melted and fully incorporated. Season with kosher salt and freshly cracked black pepper. The sauce should be thick enough to generously coat the back of a spoon, similar to a thick cream-of-mushroom soup. If necessary, add a splash of additional half-and-half to loosen it.
Preheat the oven to 375°F. Add the drained green beans to a deep 9x13-inch baking dish. Fold the crispy bacon into the mushroom Parmesan sauce, reserving a small handful for topping if desired. Pour the sauce over the green beans and gently toss until everything is evenly coated.
Transfer the casserole to the oven and bake covered for 35-40 minutes, until hot and bubbling around the edges.
Sprinkle the crispy fried onions evenly over the casserole, along with additional Parmesan if desired. Return to the oven for another 5–10 minutes, until the topping is golden brown and crispy. Top with the additional crispy bacon.
Allow the casserole to rest for 10 minutes before serving so the sauce can settle and thicken slightly.

Notes

Make Ahead Directions: You can assemble the casserole up to 24 hours in advance, leaving off the crispy fried onions. Cover tightly and refrigerate. When ready to serve, bake at 375°F for approximately 35–45 minutes, or until heated through to 165°F, adding the crispy onions during the final 5–10 minutes.

For the best texture, I prefer storing the green beans and sauce separately until the day of serving. This prevents the beans from soaking up too much sauce and becoming overly soft.

Drain the Green Beans Thoroughly: This is one of the most important steps! Excess water from the blanched green beans can thin out the cream sauce while baking. Make sure they're well drained and patted dry before assembling.

Don't Rush the Mushrooms: Allow the mushrooms to cook until most of their liquid has evaporated and they begin to brown. This concentrates their flavor and helps prevent a watery casserole.

Thicken the Sauce Before Baking: The mushroom Parmesan sauce should already be thick and creamy before adding it to the green beans. Don't rely on the oven to thicken a thin sauce.

Use Freshly Grated Parmesan: Fresh Parmesan melts more smoothly into the sauce than pre-shredded cheese and gives it a richer flavor.

Add the Crispy Onions Last: Wait until the final 5–10 minutes of baking to add the crispy fried onions so they stay crunchy and don't burn.

Adjust the Sauce Consistency: With ½ cup flour and 3 cups of liquid, the sauce will be quite thick. If necessary, add chicken broth or half-and-half a few tablespoons at a time until the green beans can be generously coated without the sauce becoming pasty.

Storage & Reheating:

Refrigerator: Store leftover casserole in an airtight container in the refrigerator for up to 3–4 days.

Reheating: Cover with foil and reheat in a 350°F oven for approximately 15–25 minutes, depending on the portion size, until heated through to 165°F. Remove the foil for the final few minutes to help crisp the topping. Add fresh crispy onions if desired.