Creating the Green Bean and Potato Casserole is an easy process if you follow these steps:

1. Preheat Oven: Set your oven to 350°F (175°C) to preheat.
2. Prep Vegetables: Peel and slice the potatoes thinly. Trim the green beans and chop the onion.
3. Sauté Onion: In a skillet over medium heat, add olive oil and sauté the chopped onion until translucent, about 5 minutes.
4. Combine Ingredients: In a large bowl, mix together the sour cream, cream of mushroom soup, garlic powder, salt, and pepper. Stir in the sautéed onion.
5. Layer Vegetables: In a greased 9×13-inch baking dish, layer half of the sliced potatoes and green beans. Pour half the sour cream mixture over the vegetables.
6. Repeat Layers: Add the remaining potatoes and green beans, then pour the rest of the mixture on top.
7. Add Cheese: Sprinkle the shredded cheddar cheese evenly over the top of the casserole.
8. Optional Topping: For a crunchy texture, you may add bread crumbs over the cheese layer.
9. Bake: Place the casserole in the preheated oven and bake for 30-40 minutes or until the potatoes are tender and lightly browned.
10. Cool and Serve: Once baked, let the casserole cool for about 15 minutes before serving. This allows the flavors to meld beautifully.

These simple steps will guide you in creating an incredible casserole that everyone will rave about!