Deliciously Creamy Custard Slice Delight 10/10

This delicious and easy vanilla custard slice has a creamy vanilla custard filling that is placed between two layers of puff pastry and topped with a simple icing glaze. It’s a classic dessert!

I was very happy to find custard squares available when we moved to New Zealand. Seeing this dessert, which I grew up with, made exploring new stores feel a bit easier.

However, most custard squares or vanilla custard slices here in Christchurch have a thick layer of icing and are sprinkled with desiccated coconut. This isn’t exactly what I’m used to, but it’s still really tasty!

In Australia, custard slices are often called “vanilla slices.”

Since vanilla custard slices were a big part of my childhood and are popular in New Zealand and Australia, I decided it was time to share a recipe for them!

Why You Will Love This Vanilla Custard Slice

It’s quick and easy to make!

This recipe uses store-bought puff pastry, making it even easier.

The thick custard center is always a success!

The creamy custard filling is placed between two layers of puff pastry and topped with a sweet glaze.

It will bring back fond memories of your childhood.

Ingredients

Here are the ingredients, notes, and possible substitutions for the vanilla custard slice/square. Please see the recipe card for quantities.

Store-bought puff pastry
I used Edmonds puff pastry because I think it’s the best option we can get in New Zealand. But you can use any brand you like. I prefer the ready-rolled sheets because they are easier to use.

Milk
I used whole milk for the custard filling. This recipe uses only milk, not cream. Milk is also used to make the vanilla icing glaze.

Butter
Butter is used instead of cream, which adds a rich taste to the custard filling.

Custard Powder
Custard powder is common in New Zealand (my favorite is Edmonds Custard Powder) and is also found in Australia, the UK, and South Africa. It’s a mix of cornstarch (called cornflour in some countries) and custard flavors. You cook it with milk and sugar to make instant custard.

Eggs
Eggs add flavor and help set the custard filling.

Sugar
Plain, regular white granulated sugar is used to sweeten the custard filling. White sugar doesn’t overpower the subtle custard flavors.

Vanilla Extract
Vanilla extract is used to flavor both the custard filling and the icing glaze.

Icing Sugar
Icing sugar (also known as powdered sugar or confectioner’s sugar) is used for the icing glaze.

Room Temperature Ingredients

Use ingredients that are at room temperature! This helps them mix together better. Room temperature is about 20°C (68°F).

To quickly bring eggs to room temperature, place them in warm water for about 10 to 15 minutes.

To soften butter quickly, cut it into cubes and microwave at 20% power in 10-second intervals. Alternatively, place the cubes in a bowl over warm water (like a double boiler) on low heat for 1 minute.

To bring milk, buttermilk, or cream to room temperature, microwave in 10-second intervals at 20% power. You can also warm them on low heat for 1 to 2 minutes, stirring every 10 to 15 seconds.

Weighing & Measuring Ingredients

Weighing ingredients with a kitchen scale is more accurate than using measuring cups. All my recipes are developed and tested using grams only.

However, check out the recipe card for cup measurements. For these conversions, cups are equal to 240 millilitres/8 fluid ounces, tablespoons are 15 milliliters and teaspoons are 5mL.

How to Make Vanilla Custard Slices

Step 1 – Prep the Cake Tin
Line an 8″x8″ square cake tin with tin foil or baking paper, leaving some overhang. This makes it easier to remove the custard slice once it’s set. Set the cake tin aside.

TIP: Before lining the tin, cut out a piece of baking paper the size of the inside of the tin. Place this template on top of the baked pastry to make trimming easier.

Step 2 – Roll Out the Pastry
Preheat the oven to 180°C (350°F). Line two baking sheets with baking paper. Roll out the pastry to about 5mm thick and at least 1 inch (2.5cm) wider than the cake tin.

Step 3 – Bake the Pastry
Place the pastry on the lined baking sheets. Prick the pastry all over with a fork, about 2cm apart. Bake for 25 to 30 minutes, or until golden brown. Remove from the oven and let cool.

NOTE: Pricking the pastry helps it rise evenly and prevents it from puffing up too much.

Step 4 – Trim the Pastry
Once cooled, trim the pastry to fit inside the cake tin using a bread knife. Place one pastry sheet at the bottom of the tin. Set the other sheet aside for later.

Step 5 – Heat the Milk
In a medium-large saucepan, heat the milk and vanilla extract until boiling. This should take a few minutes.

TIP: Prepare all ingredients before starting to cook the custard, as the process goes quickly.

Step 6 – Combine the Eggs, Water, and Custard Powder
While the milk heats, whisk together the eggs and water. Add the custard powder and whisk until smooth.

NOTE: Adding custard powder to the eggs first can create lumps, so it’s important to follow this order.

Step 7 – Add the Sugar
Once the milk boils, remove it from the heat. Stir in the sugar and whisk until dissolved.

Step 8 – Add the Custard Egg Mix
Slowly pour the egg mixture into the hot milk, whisking continuously until fully combined.

Step 9 – Cook the Custard
Return the mixture to the heat and cook while whisking constantly until it thickens, about 7 to 10 minutes.

Step 10 – Add the Butter
Remove the custard from the heat. Add the butter in small pieces, whisking each piece until fully melted and mixed in before adding the next.

Step 11 – Assemble the Slice
Pour the custard over the pastry in the cake tin and smooth it out. Place the second pastry sheet on top and gently press it down into the custard. Cool at room temperature for an hour, then refrigerate for 3 to 4 hours or overnight.

TIP: Allow the custard to set fully before removing from the tin to avoid a mess.

Step 12 – Make the Icing
Once set, whisk together icing sugar, vanilla, and milk (start with 4 tablespoons and add more if needed) until you have a pourable glaze. Pour it over the custard slice and let it set for an hour.

Step 13 – Enjoy the Slice
Use the overhangs to lift the slice from the tin. Cut with a bread knife.

Pro Tips for this Recipe

Ingredients

Gather and measure all the ingredients for the custard before you start. This helps ensure a smooth and creamy custard filling.

Ovens

The temperatures given are for conventional ovens. If you’re using a convection, fan-forced, fan-assisted oven, or an air fryer, lower the temperature by 20°C (25°F).

Always preheat your oven fully and place the rack in the middle. Try to open the oven as little as possible while baking. For the best results, use an oven thermometer.

Keep in mind that all ovens can vary, so you might need to adjust baking times based on your specific oven.

Bakeware

Metal bakeware works best for baking biscuits, cookies, brownies, muffins, quick breads, scones, and cakes because it heats up and cools down quickly. Glass bakeware is heavier, heats up and cools down slower, making it better for bread puddings, pies, crisps, crumbles, and cobblers.

Storage and Freezing

Store these custard slices in an airtight container in the fridge for up to 3 days.