Start by preheating your oven to 350°F (175°C). Roll out your pie crust and place it in a pie pan. Use the egg wash to brush the edges. This helps the crust turn golden brown and adds beautiful color. Bake it for about 20-25 minutes, or until it’s done. Let it cool completely.

In a small saucepan, over low heat, melt the chopped chocolate. Stir occasionally to prevent burning. Once melted and smooth, remove it from heat and set aside to cool slightly.

In a large mixing bowl, beat the softened butter until it’s light and fluffy. This process takes about 3-5 minutes. Your arm might get sore, but trust me, it's worth it!

Gradually add the sugar to the whipped butter, mixing well. You want it to become light and airy. Now, add in the vanilla extract and the slightly cooled melted chocolate. Beat the mixture until it’s combined smoothly.

One at a time, add the eggs into the chocolate mixture. Beat well after each addition, ensuring each egg is incorporated before adding the next. This step is crucial for achieving that signature silky texture.

In a separate bowl, whip the heavy cream until stiff peaks form. Carefully fold one-third of this whipped cream into the chocolate mixture to lighten it up. Then, gently fold in the rest of the cream, being cautious to maintain its fluffiness.

Pour the chocolate mousse filling into the cooled pie crust. Smooth the top with a spatula to create an even surface. Cover it with plastic wrap and refrigerate for at least 4 hours or overnight, allowing it to set properly.

Before serving, whip together the remaining heavy cream, powdered sugar, and vanilla extract until stiff peaks form. Spread or pipe it over the pie as a luscious topping. You can garnish with chocolate curls or shaved chocolate for that fancy touch!