Step 1: Prepare the Vanilla Custard

In a medium saucepan, combine the sugar, cornstarch, and salt. Gradually whisk in the milk until smooth. Place the saucepan over medium heat and cook while stirring constantly. Continue cooking until the mixture begins to thicken.

In a separate bowl, whisk the egg yolks. Slowly add a small amount of the hot milk mixture into the egg yolks while whisking continuously. This process tempers the eggs and prevents scrambling.

Gradually pour the tempered egg mixture back into the saucepan. Continue cooking for another 2 to 3 minutes until the custard becomes thick and creamy.

Remove from heat and stir in vanilla extract and butter. Mix until smooth. Transfer to a bowl and cover with plastic wrap directly touching the surface to prevent a skin from forming. Refrigerate for at least 1 hour.

Step 2: Prepare the Hawaiian Rolls

Using a serrated knife, carefully slice the Hawaiian rolls horizontally without completely separating the tops from the bottoms. Think of creating a pocket for the filling.

Arrange the rolls in a baking dish or on a serving tray. Brush the tops lightly with melted butter to enhance their flavor and appearance.

Step 3: Fill the Rolls

Once the custard has completely cooled, transfer it to a piping bag or a zip-top bag with the corner cut off.

Generously pipe the vanilla custard into each roll pocket. Be careful not to overfill, but ensure every roll contains a substantial amount of cream.

Smooth any excess filling and arrange the stuffed rolls neatly.

Step 4: Make the Chocolate Topping

Place the chocolate chips into a heat-safe bowl.

Heat the heavy cream until it begins to simmer but does not boil. Pour the hot cream over the chocolate chips and allow it to sit for 2 minutes.

Add the butter and whisk until the mixture becomes smooth, glossy, and fully combined.

Allow the ganache to cool slightly until it reaches a pourable consistency.

Step 5: Add the Chocolate Layer

Spoon or drizzle the chocolate ganache generously over the tops of the stuffed Hawaiian rolls.

Spread gently using the back of a spoon to ensure even coverage.

Allow the chocolate to set for approximately 15 to 20 minutes before serving.

Step 6: Chill for Best Results

For the most authentic Boston cream pie flavor, refrigerate the rolls for 30 to 60 minutes before serving.

This allows the custard to firm up and the chocolate topping to set beautifully.

Step 7: Garnish and Serve

Before serving, garnish with powdered sugar, chocolate curls, or fresh berries if desired.

Serve chilled or slightly cool for the best texture and flavor.