Brought this to a potluck and the entire crowd went nuts!

1 pre-baked 9-inch pie crust
1 cup granulated sugar
1/3 cup all-purpose flour
1/4 cup unsweetened cocoa powder
1/4 teaspoon salt
3 cups whole milk
4 large egg yolks, beaten
2 tablespoons unsalted butter
1 teaspoon vanilla extract
Whipped cream, for topping
Chocolate shavings, for garnish

In a medium saucepan, whisk together the sugar, flour, cocoa powder, and salt.

Gradually whisk in the milk until the mixture is smooth.

Cook over medium heat, stirring constantly, until the mixture thickens and comes to a boil.

Reduce the heat to low and cook for an additional 2 minutes, stirring constantly.

Remove from heat and gradually whisk about 1 cup of the hot mixture into the beaten egg yolks.

Return the egg yolk mixture to the saucepan and bring to a gentle boil, stirring constantly.

Cook for 2 more minutes, then remove from heat.

Stir in the butter and vanilla extract until the butter is melted and the mixture is smooth.

Pour the chocolate filling into the pre-baked pie crust.

Cover with plastic wrap, pressing it directly onto the surface of the filling to prevent a skin from forming.

Refrigerate for at least 4 hours or until set.

Before serving, top with whipped cream and garnish with chocolate shavings.