In a large skillet, heat a drizzle of olive oil over medium heat. Add the diced mushrooms and onion, sautéing until the mushrooms are tender and the onions are translucent, about 5-7 minutes. Add the minced garlic and sauté for another minute, until fragrant. Remove from heat and allow to cool slightly.
In a mixing bowl, combine the diced hard-boiled eggs, fresh dill, mayonnaise, Dijon mustard, lemon juice, salt, and pepper. Mix until well combined.
Once the sautéed mushrooms and onions have cooled, gently fold them into the egg mixture. Be careful not to mash the eggs; you want to keep the texture light and fluffy.
Give your Mushroom and Egg Salad a taste, and adjust the seasoning with more salt, pepper, or lemon juice as needed. The flavors should be vibrant and balanced.
For the best flavor, cover the salad and refrigerate for at least 30 minutes before serving. This allows the flavors to meld beautifully. Serve chilled on a bed of greens, in a sandwich, or alongside crackers.
