Add the water and green beans to a large skillet with a lid, over medium-high heat. Bring the water to a boil, cover, and cook for 4-5 minutes. Stop to stir or shake the green beans 1-2 times as needed. Transfer the green beans to an ice bath to stop the cooking process and drain the water from the pan. Transfer to a paper towel and pat gently to dry.

Melt the butter in the same saucepan over medium heat. Add the shallot and cook for 1-2 minutes, until translucent. Add the garlic and cook for another minute, until fragrant.

Turn the heat down to medium-low and add the green beans. Toss to coat in the shallots and garlic. Add the lemon juice, salt, pepper, and chopped parsley and toss to coat. Remove from the heat and serve with grated parmesan cheese and finely chopped walnuts.