📖 Instructions

1. Prep Your Veggies: First, get those green beans ready. If you're using fresh, snap off the tough ends and give them a good rinse. For frozen, no need to thaw them beforehand. Set aside.
2. Blanch Green Beans (if fresh): Bring a large pot of salted water to a rolling boil. Add the fresh green beans and blanch for about 4-5 minutes, or until they're bright green and tender-crisp. You want them cooked but still with a slight bite. Immediately drain and plunge them into an ice bath to stop the cooking process and preserve that vibrant color. Once cooled, drain well and pat dry. If using frozen, skip this step and add them directly in Step 8.
3. Sauté Aromatics: In a large, oven-safe skillet or Dutch oven (one that can go from stovetop to oven), melt 2 tablespoons of butter or heat 2 tablespoons of olive oil over medium heat. Add the chopped onions and cook, stirring occasionally, for about 5-7 minutes until they become soft and translucent, but don't let them brown too much.
4. Add Mushrooms and Garlic: Toss in the sliced mushrooms. Increase the heat slightly to medium-high. Cook for 8-10 minutes, stirring occasionally, until the mushrooms release their liquid and then start to turn golden brown. They should have a nice, rich color. Add the minced garlic during the last minute of cooking, stirring constantly until fragrant, about 30 seconds. Be careful not to burn the garlic!
5. Make the Roux: Sprinkle the flour over the cooked mushroom and onion mixture. Stir continuously for 1-2 minutes, allowing the flour to cook out a bit; this is your roux, thickening agent. It should form a paste-like coating over the veggies.
6. Build the Sauce: Gradually pour in the vegetable broth and heavy cream, whisking constantly to prevent lumps from forming. Bring the mixture to a gentle simmer, still whisking. It will start to thicken nicely. Reduce the heat to low.
7. Season the Sauce: Stir in the dried thyme, dried rosemary, salt, and black pepper. Taste the sauce and adjust seasonings as needed. This is your chance to make it perfect! If it feels a little too thick, you can add a splash more broth or cream.
8. Combine with Green Beans: Gently fold in the blanched (or thawed frozen) green beans until they are evenly coated in the rich mushroom sauce. Make sure every bean is happy!
9. Prepare for Baking: If your skillet isn't oven-safe, transfer the green bean mixture to a 9x13 inch baking dish. If it is, great! Sprinkle the remaining 2 tablespoons of crispy fried onions (or a portion of them) over the top of the casserole. This layer gets baked into the sauce for extra flavor and texture.
10. Bake: Bake in the preheated oven for 20-25 minutes, or until the casserole is bubbly around the edges and heated through.
11. Add Final Topping: Remove the casserole from the oven. Sprinkle the remaining crispy fried onions (if you held some back) over the top. Return to the oven for another 5-7 minutes, or until the onions are golden brown and perfectly crisp. Watch them closely so they don't burn!
12. Rest and Serve: Let the casserole rest for 5-10 minutes before serving. This allows the sauce to set a bit and makes for easier scooping. Serve warm and enjoy your elevated classic!