• Mix the sugar, cocoa powder, cornstarch and salt in a medium to large (I use a 3 ½ quart) saucepan off heat.
• Gradually whisk in evaporated milk until blended. Try to blend it as evenly as possible to avoid lumps.
• Set the pan over medium heat and stir constantly until mixture comes to a boil. After mixture starts to boil, set timer for 1 minute and continue stirring until timer goes off.
• Remove from heat. Add butter and vanilla, stirring until butter is melted. Pour into prepared crust. If your crust doesn't seem like it's going to accommodate all the filling, hold some back. Also, if you prefer a smoother filling feel free to strain it into the pie crust. I don't usually bother and we like it unstrained, but pushing it through a sieve will remove any lumps, the whipped cream covers other imperfections.
• Cover with plastic wrap or buttered parchment to prevent skin from forming. Let the pie cool at room temperature for about an hour, then transfer to the refrigerator.
• Chill 4 hours or until ready to eat.

Homemade Whipped Cream

• Before you serve the pie, top it with store-bought whipped topping or make your own using 1 cup of whipping cream and about ⅓ cup of sugar. This will give you plenty, probably more than you need for the top of the pie.
• To make whipped cream, combine the whipped cream and sugar in the bowl of a stand mixer and beat just until soft peaks form. Add vanilla and keep whipping just until peaks are stiff.