Prepare Green Beans: Preheat the oven to 375°F (190°C). In a large pot of boiling water, cook the green beans for 3–4 minutes until just tender. Drain and set aside.

Sauté the Vegetables: In a large skillet over medium heat, sauté the sliced onions until they start to caramelize, about 5–6 minutes. Add the mushrooms and garlic, cooking for an additional 3 minutes until the mushrooms soften. Season with a pinch of salt and pepper.

Add the Cream Cheese: Reduce heat to low and add the cream cheese, stirring until melted and evenly coating the vegetables.

Combine and Bake: Add the blanched green beans to the skillet, stirring everything together until well mixed. Transfer the mixture to a casserole dish, spreading evenly. Sprinkle shredded cheddar cheese on top.

Bake: Place the casserole in the preheated oven and bake for 15–20 minutes, or until the cheese on top is bubbly and golden.

Serve: Let the casserole cool slightly before serving. Enjoy as a deliciously creamy, cheesy side dish alongside your favorite main course.