Lemon Biscuit Slice (No-Bake)

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My no-bake lemon biscuit slice is the perfect summer sweet treat. It has a crunchy digestive base and a sweet zesty topping.

stack of 2 squares of no bake lemon biscuit slice

I recently created a collection of all the no-bake biscuit slice recipes I've made for the blog so far, and today I thought I'd add another: this easy no-bake lemon biscuit slice!

It tastes like lemon drizzle cake with the zesty icing to match, but it's perfect for summer because you can make it without having to turn the oven on! It's quick and easy and great for any occasion. I hope you enjoy it!

Ingredients

Digestive biscuits: These neutral-flavoured biscuits will create a nice crunchy base while allowing the lemon flavour to shine.
Butter: Use real butter for this recipe, not margarine.
Condensed milk: This is the thick, sweetened version. If you've never used it before, check out my post on the difference between condensed milk and evaporated milk.
Lemon extract: For the biscuit base.
Icing sugar: Just like a classic lemon drizzle cake, this biscuit traybake is going to be topped with a thin layer of lemony icing.
Yellow food colouring: Optional but adds a fun pop of colour!
Fresh lemons: We'll use some lemon juice in the icing, plus lemon zest on top. You'll need 2-3 lemons for this recipe.

Equipment

8x8 tin: This is my favourite size of tin to use for biscuit slices. If you don't have this size, you can adjust the recipe to fit your tin using my cake tin converter.
Baking paper: To line the tin. Make sure to get the edges too, not just the bottom!
Saucepan or heatproof bowl: To melt the butter for the base.
Mixing bowls: You'll need a large one for mixing the biscuit base and a small one to make the icing.
Utensils: A teaspoon and a tablespoon for measuring, a wooden spoon for mixing, a sharp knife for cutting and a microplane grater for zesting the lemons.
Food scale: For accurate results, weigh out your ingredients in grams unless otherwise stated, as this is how I test all of my recipes.

slices of no bake lemon biscuit traybake on a white surface

How to make lemon biscuit slice step-by-step

Step 1: As with all my other no-bake biscuit traybakes, we'll start by lining an 8x8-inch tin with baking paper. Check out my post on how to line a traybake tin properly.

Step 2: Next, add 450g of digestive biscuits to a food processor or high-powered blender. Blitz them up until you have fine crumbs. You can run your fingers through to check there are no large lumps left behind.

Step 3: Pour the biscuit crumbs into a large mixing bowl along with 120g melted butter, 120ml (~150g) condensed milk and 3 teaspoons of lemon extract to taste. Mix well until you have a paste-like mixture.

Step 4: Transfer the biscuit mixture into your lined tin and use a small spoon to press it down nice and evenly.

Step 5: Prepare the topping by mixing 3 tablespoons of lemon juice into 200g of icing sugar. To make it runnier, add more lemon juice, and to make it thicker, add more icing sugar.

Step 6: Optionally, you can add 1-2 tablespoons of icing to a small bowl and stir in a few drops of yellow food colouring.

Step 7: Spoon the white icing over the biscuit base and spread it out neatly. Then swirl in the yellow icing using a toothpick.

spreading white icing on top of the biscuit base

decorating the lemon traybake with lemon zest

Step 8: Top with some lemon zest and pop it in the fridge for about 4 hours to set.

Step 9: Once set, remove your lemon slice from the tin, cut it into squares and enjoy! I usually cut mine into 9 squares then cut those in half to make 18 rectangles or triangles, but you can make yours as big or as small as you like.

Top tips

Measure the butter with a scale first, then melt it. Proper measuring will help to prevent a soggy base.
If you don't have lemon extract, you can swap this out for 1-2 tablespoons of lemon zest in the base.
Always line the sides of the tin too, so the icing doesn't 'glue' itself on there! This will help you get clean edges.
Gel food colouring will work best- you only need a few drops.

FAQs

How long will my lemon biscuit slice last?

This will keep well for about 1 week. For maximum storage time, keep it in an airtight container in the fridge.

Can I freeze it?

Yes, this no-bake lemon slice is great for freezing and it defrosts well. You can freeze the entire slab on a baking tray until it's solid then wrap it tightly in clingfilm, or you can pop individual slices into airtight containers, using small pieces of baking paper to prevent them from sticking together. To defrost, transfer it to the fridge overnight.

What can I use instead of icing?

If you don't fancy icing, you can make some lemon fudge by mixing the rest of the tin of condensed milk (~250g) with 250g white chocolate, 3-4 teaspoons of lemon extract and a splash of yellow food colouring. You can also make a simple chocolate topping by mixing 250g white chocolate with 2-3 teaspoons of lemon extract.

Can I make this traybake gluten-free?

Yes! Just swap out the digestives for a gluten-free alternative, and double-check the rest of the ingredients for cross-contamination risks, as this varies from brand to brand.

overhead image of no bake lemon drizzle biscuit slice

More biscuit slices

I hope you like my no-bake lemon biscuit slice! If you try it at home, please leave a rating and comment below. Enjoy!