I have this vivid memory from when I was a kid. My grandma would take me to the local bakery, and my eyes would be glued to the glass cabinet, trying to decide.
But my gaze always landed on the custard slice. That perfect yellow slab with a crumbly base and a simple icing top. It was pure magic.
For years, I thought it was some complicated secret only bakers knew. Turns out, it’s one of the simplest, most satisfying desserts you can make right at home.
And the best version? The one that doesn’t even require you to turn on the oven. This is that recipe. It’s my go-to for a guaranteed crowd-pleaser that tastes like nostalgia.
What You’ll Need
Here are the simple ingredients that come together to create this classic treat. You probably have most of them in your pantry already.
For the Biscuit Base:
- 250g (8.8 oz) plain sweet biscuits (like Arnott’s Marie or digestive biscuits)
- 125g (1/2 cup) unsalted butter, melted
For the Custard Filling:
- 60g (1/2 cup) custard powder
- 800ml (3 1/3 cups) full-cream milk, divided
- 110g (1/2 cup) caster sugar
- 60g (1/4 cup) unsalted butter, softened
- 1 tsp vanilla extract
For the Passionfruit Icing:
- 190g (1 1/2 cups) icing sugar (confectioners’ sugar)
- 2 tbsp passionfruit pulp (canned or fresh)
- 20g (1.5 tbsp) unsalted butter, melted
Tools Required for the Job
You don’t need any fancy equipment for this recipe, just a few kitchen basics.
- 20cm x 20cm (8×8 inch) square baking tin
- Baking paper (parchment paper)
- Food processor or a zip-top bag and rolling pin
- Medium saucepan
- Whisk
- Spatula
- Measuring cups and spoons
Step-by-Step Instructions
Follow these simple steps for a perfect custard slice every time. We’ll build it layer by layer.
Part 1: The Biscuit Base
Step 1: First, prepare your tin. Grease your 8×8 inch square tin and line it with baking paper, leaving some overhang on the sides. This is your secret weapon for lifting the slice out later.
Step 2: Crush the biscuits into a fine crumb. You can do this quickly in a food processor or place them in a zip-top bag and crush them with a rolling pin (a great way to get some frustration out!).
Step 3: Pour the melted butter over the biscuit crumbs and mix until it looks like wet sand. Make sure every crumb is coated.
Step 4: Tip the mixture into your prepared tin. Use the back of a spoon or the bottom of a glass to press it down firmly and evenly. This is key to a base that doesn’t fall apart. Pop it in the fridge to chill while you make the custard.
Part 2: The Creamy Custard Filling
Step 5: In a small bowl, whisk the custard powder with 1/2 cup of the milk until you have a completely smooth, lump-free paste. Take your time with this step; it prevents lumpy custard.
Step 6: Pour the remaining milk and the caster sugar into a medium saucepan. Heat over medium heat, stirring, until the sugar has dissolved and the milk is just about to simmer. Don’t let it boil over!
Step 7: Remove the saucepan from the heat. Slowly pour the custard paste into the hot milk, whisking constantly as you pour. This tempers the mixture and ensures a silky texture.
Step 8: Return the saucepan to the heat. Cook, whisking continuously, for about 5-7 minutes. The custard will thicken significantly. You’re looking for a very thick consistency that plops off the whisk.
Step 9: Once thick, take it off the heat and whisk in the softened butter and vanilla extract until smooth. The butter adds a wonderful richness.
Step 10: Pour the hot custard over your chilled biscuit base and smooth the top with a spatula. It will start setting quickly, so work fast.
Step 11: Let it cool on the counter for about 30 minutes, then cover with plastic wrap (press it directly onto the surface of the custard to prevent a skin from forming) and refrigerate for at least 4 hours, but overnight is best. It needs to be completely firm.
Part 3: The Tangy Icing
Step 12: Once the custard is fully set, make the icing. Sift the icing sugar into a bowl to get rid of any lumps.
Step 13: Add the melted butter and passionfruit pulp. Mix until you have a smooth, spreadable icing. If it’s too thick, add a tiny bit more passionfruit pulp or a few drops of water. If it’s too thin, add a bit more icing sugar.
Step 14: Pour the icing over the set custard and spread it evenly. Place the slice back in the fridge for another 30 minutes to an hour for the icing to set.
Step 15: To serve, use the baking paper overhangs to lift the whole slice out of the tin. For clean cuts, use a large, sharp knife dipped in hot water and wiped dry between each slice.
Pro Tips From My Kitchen
Over the years, I’ve learned a few things that make this recipe foolproof.
- Lump-Free Guarantee: Seriously, don’t rush mixing the custard powder and cold milk. Creating a perfectly smooth slurry at the start is the number one secret to a silky, lump-free custard filling.
- The Base Press: Don’t just pat the biscuit base down. Really press it firmly into the corners and across the bottom. A solid, compact base is what holds everything together when you slice it.
- Patience is a Virtue: The hardest part of this recipe is waiting. Don’t try to ice or slice the custard before it’s completely cold and firm. An overnight chill is your best bet for perfect, sharp slices.
- Hot Knife Trick: For those bakery-perfect slices, run a large knife under hot water, wipe it completely dry with a paper towel, and then make a cut. Repeat for every single cut. It makes a world of difference.
Substitutions and Variations
One of the great things about this recipe is how adaptable it is. Here are a few ideas to get you started.
| Component | Substitution Idea | Notes |
|---|---|---|
| Biscuits | Graham Crackers or Shortbread | Adds a different flavor profile. |
| Icing | Chocolate Ganache | Melt 100g dark chocolate with 100ml cream. |
| Milk | Almond or Soy Milk | For a dairy-free version. |
| Flavor | Lemon Zest | Add zest of 1 lemon to the custard. |
Make it Gluten-Free
Simply use your favorite brand of gluten-free plain sweet biscuits for the base. The rest of the ingredients are typically gluten-free, but always double-check your custard powder label to be sure.
Nutritional Info & Meal Suggestions
While this is a dessert, it’s good to have a rough idea of its nutritional content. Here is an approximation per slice (if cut into 16 squares).
| Nutrient | Approximate Amount |
|---|---|
| Calories | 250-300 kcal |
| Carbohydrates | 35g |
| Fat | 12g |
| Protein | 4g |
Disclaimer: These values are estimates and can vary based on the specific ingredients used.
Pairing and Efficiency
This custard slice is perfect on its own, but it truly shines alongside a hot cup of tea or a simple black coffee. The bitterness of the drink cuts through the sweetness of the slice beautifully.
To be efficient, get all your ingredients measured and ready before you start. While the base is chilling, you can make the custard. The long chilling time is hands-off, so you can make this a day before you plan to serve it.
Make-Ahead and Storage Tips
This is an ideal make-ahead dessert. You can prepare the entire slice up to 2 days in advance and keep it covered in the refrigerator. The flavors will meld together even more.
Store any leftovers in an airtight container in the fridge for up to 4 days. I do not recommend freezing it, as the custard can become watery and grainy upon thawing.
Frequently Asked Questions
Q1. Why did my custard turn out lumpy?
Ans: This usually happens for two reasons. Either the custard powder wasn’t mixed into a completely smooth paste with the cold milk at the start, or the paste was added to the hot milk too quickly without constant whisking.
Q2. My biscuit base is too hard/too crumbly. What went wrong?
Ans: If it’s too hard, you might have pressed it down with too much force. If it’s too crumbly, you might not have used enough butter to bind the crumbs, or you didn’t press it down firmly enough. It’s a bit of a balancing act!
Q3. Can I use instant pudding mix?
Ans: I wouldn’t recommend it for this recipe. Custard powder needs to be cooked to activate its thickeners, which results in a dense, sliceable custard. Instant pudding is designed to set cold and will give you a much softer, pudding-like texture that won’t hold its shape.
Q4. My slice isn’t setting properly. How can I fix it?
Ans: This almost always comes down to two things: the custard wasn’t cooked long enough to become thick, or the slice hasn’t been chilled for long enough. Give it more time in the fridge; an overnight chill is usually the magic cure.
Wrapping Up
And there you have it. The secret to that iconic bakery-style custard slice is out, and it’s been hiding in your pantry all along.
It’s more than just a dessert; it’s a slice of comfort. It’s perfect for afternoon tea, a family gathering, or just because you deserve a treat.
I really hope you give this recipe a try. When you do, come back and leave a comment below. I’d love to hear how it turned out for you or if you added your own unique twist!
