Fill a skillet with hot water until it's about halfway full.
Bring it to a boil over high heat, then reduce the heat to keep it at a simmer.
In a bowl, lightly beat the eggs with milk, salt, and pepper.
Heat olive oil in a skillet over medium-high heat.
Add the mushrooms and cook for about 1-2 minutes until they start to brown.
Stir in the parsley and garlic, cooking for a few seconds before removing the skillet from the heat.
Add the egg mixture to the mushroom skillet.
Place the skillet in the larger skillet with simmering water (double boiler method).
Continuously stir the mixture with a wooden spoon until the eggs are set but still soft.
Remove from heat.
Spoon the egg and mushroom mixture onto each slice of bread.
Notes / Tips / Wine Advice:
This updated version keeps the essence of the original recipe from the Basque city of Vitoria, offering a flavorful, garlicky mushroom and egg topping for a delightful canapé experience.