Vegan Vanilla Slice

Close up of vanilla slice on a plate. The slice has two flaky layers of puff pastry sandwiching a thick layer of custard.

This vegan vanilla slice (or custard slice) is just like the classic bakery treat but with NO dairy or eggs! It has a thick layer of creamy custard between two layers of puff pastry, and is topped with an optional icing.

Course Dessert

Cuisine Australian, New Zealand

Prep Time 15

Cook Time 30

Total Time 45

Servings small squares

Calories 236

Author Anthea

Ingredients

Vegan Vanilla Slice

2 sheets frozen vegan puff pastry thawed (note 1)
1 ¼ cups (145g) custard powder (note 2)
¾ cup (150g) sugar or caster sugar (or use 1 cup / 200g sugar if your custard powder doesn't have some sugar in it)
4 cups (1000g or 1L) dairy-free milk such as soy or oat
½ cup (125g) vegan spreadable butter or vegan block butter (note 3)
2 teaspoons vanilla paste or vanilla extract

To decorate (see note 4 for icing options)

½ cup (50g) powdered sugar / icing sugar

Instructions

Prepare the pastry:

Preheat oven to 200°C (390°F) for a conventional oven, or 180°C (350°F) for a fan-forced oven.
Line 1 large baking tray with baking paper (parchment paper). Place the two sheets of frozen puff pastry on the trays and allow to thaw. If you can only fit one sheet of pastry on your baking tray, bake them after each other.
Place another sheet of baking paper on top of the pastry and another baking tray on top. Bake the pastry for 20-25 minutes or until golden and baked through. Set aside on a wire rack and allow to completely cool.
Use a sharp serrated knife to trim the pastry to fit in your baking pan. I used a 23 cm (9-inch) baking pan. Alternatively, you may use a smaller baking pan such as an 8-inch (20cm). The custard layer of your slice will just be thicker!
Line your square baking pan with baking paper with some overhanging. Place one of the trimmed pastry sheets on the bottom of your baking pan. Set aside.

Prepare the custard and assembly:

Add the custard powder and sugar to a large pot and mix until combined. Add around 1 cup of milk and whisk until smooth and there are no lumps. Add the remaining milk, the spreadable butter and vanilla.
Place the pot over medium-high heat and cook the custard for 15-25 minutes while whisking constantly. When the custard has thickened, cook it for another 3 minutes. The custard is ready when it thickly coats the back of a spoon and, if you lift your whisk, the custard should fall into thick 'ribbons'.
If your custard has any lumps in it, quickly blend it with a stick blender or strain it through a metal sieve. This will temporarily make the custard runny, which is fine (it will thicken again later).
Quickly pour the custard into your baking pan on top of the pastry. If needed, smooth the surface. Place the remaining pastry square on the top.
Cover and chill the vanilla slice in the fridge for 4 hours or ideally overnight.

Cutting the vanilla slice:

Remove the vanilla slice from the baking pan.
Use a sharp serrated knife and a gentle 'back and forth' sawing motion to cut the vanilla slice into squares or rectangles. Dust the vanilla slice generously with icing sugar.
Enjoy immediately! Store leftovers in an airtight container in the fridge for 3-4 days. The pastry will naturally soften over time. If you dusted your slice with icing sugar, it will dissolve overnight so I recommend dusting it again.

Notes

Many brands of frozen puff pastry are accidentally vegan as they contain vegetable shortening instead of butter. However, double-check the ingredients of your pastry before you buy it.
Similarly, many brands of custard powder are accidentally vegan. I used Foster Clarks custard powder but Bird's and the Woolworths brand also has a vegan-friendly custard powder. Double-check the ingredients to make sure it doesn't contain milk or egg solids. Alternatively, you can use the same amount in cornstarch / corn flour. I recommend adding a pinch of turmeric for colour. Check out the blog post for more details.
I tested this recipe with Nuttelex Buttery as it's very accessible in Australia. However, you can use any spreadable vegan butter or a vegan block butter (for a slightly firmer custard).
For passionfruit icing, combine 2 cups (300g) icing sugar, 1/4 cup (60g) melted vegan spreadable butter and 3 tablespoons (45g) passionfruit pulp. For a classic pink icing, mix 2 cups (300g) icing sugar, 1/4 cup (60g) melted vegan spreadable butter, 2 tablespoons (30g) dairy-free milk and a few drops of pink or red food colouring. Add more sugar for a thicker icing or more liquid for a runnier icing. When the vanilla slice has set, remove it from the baking pan, then ice the top. Chill it for another 30 minutes, then cut and serve.

Nutrition