1. Start by washing the green beans thoroughly, then snap or cut off the stem ends. You can leave them whole or cut them into 2-inch pieces, depending on your preference. For the mushrooms, wipe them clean with a damp paper towel or a mushroom brush to avoid excess moisture. Slice the mushrooms to about 1/4-inch thickness, or quarter them if they are very small. Finally, peel and mince the garlic cloves.

2. Bring a large pot of salted water to a rolling boil, then add the trimmed green beans and cook for 2-4 minutes. Immediately drain the green beans and plunge them into an ice bath to stop the cooking process. Once cooled, drain the green beans thoroughly and pat them dry.

3. In a large skillet or wok, heat 2 tablespoon of olive oil over medium-high heat. Add the sliced mushrooms in a single layer and let them cook undisturbed for 3-4 minutes. Stir occasionally and cook for an additional 3-4 minutes until they are golden brown. Season with salt and pepper to taste.

4. In the same skillet, add the remaining 1 tablespoon of olive oil over medium-high heat. Once hot, add the minced garlic and sauté for about 30 seconds. Then, add the blanched (or raw) green beans and sauté for 3-4 minutes until heated through.

5. Return the sautéed mushrooms to the skillet with the green beans. Add the soy sauce and toss everything together to combine. If using, stir in the butter until melted and the vegetables are coated. Taste and adjust seasoning as desired.

6. Garnish with chopped fresh parsley or chives before serving.