Preheat the oven to 350°F (175°C).

Generously grease an 8-inch glass or ceramic pie plate with butter or non-stick cooking spray.

In a large mixing bowl, cream the softened butter and granulated sugar together using a hand mixer on medium speed until the mixture is pale and fluffy, approximately 3 minutes.

Add the eggs one at a time, beating thoroughly after each addition to ensure proper aeration. Mix in the vanilla extract.

In a separate small bowl, whisk together the sifted flour, cocoa powder, and salt.

Using a spatula, gently fold the dry ingredients into the butter mixture until no white or brown streaks remain. Avoid overmixing to maintain the fudgy texture.

Pour the batter into the prepared pie plate and smooth the surface with the back of a spoon or an offset spatula.

Bake for 30 to 35 minutes. The pie is done when the edges are firm and the top has developed a thin, crackly crust, but the center remains slightly soft to the touch.

Remove from the oven and allow to rest on a wire rack for at least 10 minutes to set.

Slice and serve warm, ideally topped with a scoop of vanilla bean ice cream or a dollop of fresh whipped cream.