You can prepare these eggs up to several hours in advance. Cover tightly with plastic wrap and store in the refrigerator until ready to serve.
For a smoother texture, pulse the mushrooms and parsley in a food processor until very fine, as recommended by the original recipe.
If you prefer a lighter version, you can use reduced-fat mayonnaise, though the texture may be slightly less rich.
Plan on serving 3-4 halves per person for a generous appetizer portion.