How to Make a Custard Square, the Most Popular Dessert in New Zealand

The custard square has been a long-standing bakery classic in New Zealand (like this shortbread) for generations. It’s popular in Australia, too, where it’s known as “vanilla slice.” But this dessert deserves to gain more traction in the US.

With layers of luscious vanilla custard and flaky puff pastry, we felt it was our duty to put the recipe to the test. Here’s how to make custard square, a pastry wonder from Down Under!

What Is a Custard Square?

A custard square is a simple yet elegant pastry made with a thick layer of vanilla custard sandwiched between two layers of compressed puff pastry. The dessert is topped with a dusting of powdered sugar or a smear of sweet vanilla icing.

The exact origin of the custard square is unknown and widely contested. However, they’re often compared to France’s mille-feuille, a similar dessert that features multiple tiers of flaky puff pastry (not to be confused with phyllo dough) and elegantly piped crème pâtissière.

Don’t miss this collection of the best desserts from around the world!

Vanilla Custard Square Recipe

This recipe makes nine squares in an 8×8-inch pan.

Ingredients

Custard Slice ingredients

2 sheets frozen puff pastry
3/4 cup sugar
2/3 cup custard powder (I used Bird’s Custard Powder)
7 large egg yolks
1-3/4 cups whole milk
1 cup heavy whipping cream
2 teaspoon vanilla extract
1/3 cup unsalted butter, diced
1/2 teaspoon unflavored gelatin powder
2 tablespoons water
1/8 teaspoon salt

Tools You’ll Need

Directions

Step 1: Bake the puff pastry

puff pastry

Line an 8×8-inch metal pan with two layers of parchment paper, allowing several inches of parchment to drape over the sides. The parchment “handles” will make removing the custard square easy later.

Preheat the oven to 350°F. Arrange each puff pastry sheet on a large sheet pan lined with parchment paper. Top each piece of pastry with a second sheet of parchment paper, a second sheet pan and a heavy skillet. Bake for 20-25 minutes. Then remove the skillet, second sheet pan and the top layer of parchment and continue to bake the pastry for 5-7 minutes until golden. Remove promptly.

Editor’s Tip: If you don’t have enough sheet pans (or oven space) to bake both pieces of pastry simultaneously, bake each piece one at a time. It will take a bit longer, though.

Step 2: Trim the pastry

trim pastry

While the pastry is still warm, use a sharp knife to cut each piece of pastry into a neat square, trimming as necessary, so they fit snugly in your prepared 8×8 pan. I made a template with a spare piece of parchment paper for precision and ease.

Step 3: Warm milk and cream

To prepare the custard, bring the milk and cream to a low boil in a medium saucepan, then remove from the heat.

Step 4: Mix and temper

Custard Slice ingredients

In a mixing bowl, whisk together the egg yolks, sugar and custard powder until well combined. Then, temper the egg mixture by slowly adding half of the hot milk mixture into the bowl, whisking continuously until smooth.

Editor’s Tip: Make sure you really do whisk continuously as you temper the eggs. If you don’t keep the mixture moving, you run the risk of scrambling the eggs.

Step 5: Thicken the custard

Add the tempered egg mixture into the remaining milk in the saucepan and return it to the stove over medium heat. Stir continuously until the custard boils and thickens. It should be very thick and hold stiff ridges when stirred. Remove from heat.

Step 6: Finish the custard

Custard Slice

In a small bowl, bloom the gelatin for 2 minutes in 2 tablespoons of water. Add gelatin to the warm custard along with the butter, salt and vanilla extract. Beat rapidly with a whisk until smooth, then let cool for 5-10 minutes at room temperature.

Editor’s Tip: Make sure you fully incorporate the butter into the custard. If the custard seems to be slipping and sliding in the bowl with ease, keep mixing until the custard starts to cling to the sides of the bowl.

Step 7: Assemble the custard square

Custard Slice

Lay one square of pastry into the parchment-lined pan. Next, spread the warm custard over the puff pastry base in a smooth, even layer. Top with the second piece of puff pastry, pressing down gently to remove any air bubbles.

Step 8: Chill

Cover the pan tightly with plastic and then chill in the fridge for at least 5 hours, but overnight for best results.

Step 9: Remove and decorate

Custard Slice 011522 Toh 16 Adedit

To serve, carefully lift the whole custard square from the pan. Remove the parchment paper and then dust with powdered sugar (or try with this simple vanilla frosting).

Use a sharp serrated knife to gently saw through the top layer of pastry. Then, using a clean, sharp chef’s knife, cut through the custard and bottom layer of pastry. Enjoy!

Tips for Making a Custard Square

Custard Slice

What is custard powder?

It’s similar to what we call pudding mix in the United States. It’s a powdered mix made with egg yolks, sugar, cornstarch and flavoring that is mixed with milk and heated until it thickens into a custard. Bird’s custard powder is one of the most well-known brands and can be found in the baking aisle at some grocery stores at World Market and on Amazon.

Can I use pudding mix instead of custard powder?

Possibly! While this recipe has not been tested with pudding mix, other recipes often use a 1:1 swap with success. If you want to try this recipe using vanilla pudding mix, make sure to select a Cook & Serve pudding mix and not an instant pudding mix. If your pudding is not thickening, add a few extra teaspoons of cornstarch mixed with milk until the proper consistency is reached.

How do I store custard squares?

Store the slices in a covered container in the refrigerator. Custard squares are best eaten within 2-3 days. However, they may be kept in the refrigerator for up to 5 days.

Can you freeze custard squares?

No, this is not recommended. Egg-based custards, like the one in this recipe, tend to split and take on a funny texture once frozen and thawed. For best results, enjoy your vanilla slices within a few days.

How do you cut the squares?

This can be tricky to do without squashing custard out the sides! If you don’t have a sharp serrated knife, use a clean pair of kitchen shears or scissors to cut through the top layer of pastry and then follow up with a regular chef’s knife to slice through the custard and bottom layer of pastry.

Round out your menu with a classic New Zealand recipe for rosemary lamb shanks or lentil lamb stew.

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