Transfer all of the ingredients to a food processor in the following order: green beans, mushrooms, onions, garlic, and walnuts. Combine them well. Then, add 3 peeled hard-boiled eggs and pulse until the mixture is thoroughly combined. Taste the mixture and if you would like a milder taste and a softer texture, add the 4th hard-boiled egg. Mix the ingredients again, taste and adjust the salt and pepper according to your preference. Mix it once more. The mixture should be roughly chopped. However, if you prefer a smoother pâté-like consistency, transfer the mixture to a blender and blend until it reaches your desired texture.