If making a homemade crust, press graham cracker crumbs into a 9-inch pie dish and chill or prebake as needed.

In a medium saucepan, whisk together sugar, cornstarch, and instant coffee granules. Gradually add milk, whisking until smooth.

Cook over medium heat, stirring constantly, until thickened and bubbling. Reduce heat and cook for 1 more minute.

In a separate bowl, whisk egg yolks. Slowly add a small amount of the hot milk mixture, whisking to temper the yolks.

Pour the tempered yolks back into the saucepan and cook for 1-2 more minutes, stirring, until fully thickened.

Remove from heat and stir in chopped chocolate, butter, and vanilla extract until smooth.

Pour the mocha filling into the prepared crust, smooth the top, and cover with plastic wrap. Refrigerate for at least 4 hours until set.

In a cold mixing bowl, whip heavy cream and powdered sugar to stiff peaks.

Spread or pipe the whipped cream over the pie and garnish with cocoa powder or chocolate shavings.

Slice and serve chilled!