No Bake Boston Cream Pie Bars In One Pan

These bars copy the layers of a Boston cream pie in a sliceable pan dessert: a buttery graham cracker crust, a cooked vanilla custard, and a glossy chocolate ganache. Nothing goes in the oven. The custard is cooked briefly on the stovetop, then everything chills. Hands-on time is about 25 minutes, and the bars need roughly 3 hours in the fridge before they can be cut.

Ingredients for the Bars

The recipe makes 12 bars in a 9×13-inch pan.

Crust

• 2 cups graham cracker crumbs
• 1/2 cup unsalted butter, melted
• 2 tbsp granulated sugar

Vanilla Custard Filling

• 2 cups whole milk
• 1/2 cup granulated sugar
• 3 tbsp cornstarch
• 4 large egg yolks
• 2 tsp pure vanilla extract
• 2 tbsp unsalted butter

Chocolate Ganache Topping

• 4 oz semi-sweet chocolate, chopped
• 1/2 cup heavy cream

Whole milk and egg yolks are what give the custard its thick, pudding-like set, so use them rather than lower-fat milk. Chop the chocolate finely so it melts fully in the hot cream.

Making the Crust, Custard and Ganache

1. Prepare the crust: In a medium bowl, combine graham cracker crumbs, sugar, and melted butter. Press evenly into a 9×13-inch pan lined with parchment paper. Chill in the fridge while making the filling.
2. Make the custard: In a medium saucepan, whisk together sugar and cornstarch. Gradually whisk in milk over medium heat. Cook, stirring constantly, until the mixture thickens and bubbles.
3. Temper the yolks: In a small bowl, lightly beat egg yolks. Slowly whisk in a few spoonfuls of the hot milk mixture to temper the yolks, then return the mixture to the saucepan. Cook for 1-2 more minutes until very thick. Remove from heat and stir in butter and vanilla. Pour custard over the chilled crust. Smooth the top and refrigerate for at least 2 hours.
4. Make the ganache: Heat cream in a small saucepan until it just begins to simmer. Pour over chopped chocolate in a heatproof bowl. Let sit for 2 minutes, then stir until smooth. Pour over the set custard and spread evenly. Refrigerate for 1 hour or until firm.
5. Slice and serve: Use a sharp knife to cut into bars. Wipe the knife clean between cuts for neat edges.

Getting Clean Slices and a Smooth Custard

• Press the crust firmly. A loose crust crumbles when you cut through it. Pressing the crumbs down with the flat bottom of a measuring cup helps compact them.
• Whisk constantly. Stirring while the milk mixture heats keeps the cornstarch from clumping and the bottom from scorching.
• Temper the yolks slowly. Add only a few spoonfuls of hot milk to the yolks at first. Pouring in too much too quickly can scramble the eggs into small lumps.
• Let the custard fully set before adding the ganache. Warm custard will melt into the chocolate and leave a muddy top layer. Give it the full 2 hours.
• Warm the ganache if it stiffens. If it thickens before you spread it, warm it very gently so it spreads without tearing the custard.
• Wipe the knife between cuts. Custard and chocolate smear otherwise, and clean wipes give neat edges.

Why Boston Cream Bars Turn Out Runny or Lumpy

• Runny custard: The mixture did not cook until it thickened and bubbled. Return it to the heat, stirring constantly. For a firmer set next time, add an extra 1 tsp of cornstarch.
• Lumpy custard: Usually from scrambled yolks or undissolved cornstarch. Strain the custard through a fine sieve before pouring it over the crust.
• Soft, sliding ganache: It needs the full hour in the fridge. Cutting too early drags the chocolate.

Crust and Filling Swaps

• Different crust: Digestive biscuits or shortbread crumbs can replace graham crackers. Expect a slightly different flavor, and a buttery shortbread crust may be a little softer.
• Dairy-free: Coconut milk in the custard and coconut cream in the ganache can work, but expect a noticeable coconut flavor and a slightly softer set.
• Flavored custard: A teaspoon of espresso or liqueur stirred into the finished custard adds a little depth.

Storing and Making Ahead

These bars are best made a day ahead, since the chilling time does most of the work. Keep them covered in the refrigerator and eat them within 4 days. The custard and eggs make them perishable, so don’t leave them out for more than 2 hours. The ganache softens at room temperature, so keep the bars chilled until serving. Freezing is not recommended, because the custard can turn watery when thawed.

More Boston Cream Desserts

If you like this flavor combination, try it in a different form as a Boston cream poke cake with ganache or as Boston cream cupcakes. For another custard-style no-oven dessert, see this Southern banana pudding.

Boston Cream Pie Bar FAQ

Can I use instant pudding instead of making custard?

You can as a shortcut, but homemade custard is creamier and richer and sets with a cleaner cut.

How long do the bars keep?

Store them in an airtight container in the fridge for up to 4 days.

Why is this called no-bake?

The crust and filling never go in the oven. The custard is cooked briefly on the stovetop and the bars set in the refrigerator.

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