Photo: Craig Dugas · CC BY-SA 2.0
Nanaimo Bar (Three-Layer Chocolate Slice)
The Canadian three-layer slice that never sees an oven. Its structure is that each layer is held by a different fat: cooked egg and butter glue the crumb base, butter carrying icing sugar sets the middle firm at fridge temperature, and the cocoa butter in the chocolate crystallises into the top. Why that top shatters the moment a knife touches it — and why the butter stirred into it is structural rather than richness — is what this page is about.
Ingredients
- Layer 1 (20cm square tin, 16 pieces)
- butter115 g
- caster sugar50 g
- cocoa powder · unsweetened40 g
- egg · beaten1
- graham cracker crumbs · digestive biscuits work175 g
- desiccated coconut · unsweetened60 g
- walnuts · coarsely chopped; almonds or pecans also work60 g
- Layer 2
- butter · at room temperature115 g
- custard powder · or 2 tbsp cornflour plus vanilla2 tbsp
- milk3 tbsp
- icing sugar · sifted250 g
- Layer 3
- dark chocolate · 55-60% cocoa115 g
- butter · not optional — see the tips30 g
Steps
- ⏲ 5 min
Line a 20cm square tin with baking paper, leaving plenty hanging over two sides — you lift the whole slab out by it once it is set.
- ⏲ 5 min
Layer 1: cook it over water. Over a pan of simmering water, melt 115g butter with the sugar and cocoa, then pour in the beaten egg, stirring, and cook until it thickens, 4 to 5 minutes. This layer is set by egg, so straight over the flame it scrambles.
- ⏲ 5 min
Off the heat, stir in the crumbs, coconut and walnuts, tip into the tin and press it down firmly with the base of a glass. Not compacted, and the base crumbles when you cut it.
- ⏲ 30 min
Chill 30 minutes. As the butter sets it grips the crumbs into one slab.
- ⏲ 5 min
Layer 2: beat the custard powder and milk into the 115g of room-temperature butter, then add the icing sugar in two or three goes and beat until pale and light. It should be a pipeable cream.
- ⏲ 15 min
Spread it level over the cold base and chill at least 15 minutes, until properly cold. Lukewarm, it lets the melted chocolate of the next step sink a channel into it and the two layers merge.
- ⏲ 5 min
Layer 3: melt the 115g chocolate with the 30g butter over water and stir smooth. Use it barely melted and not hot.
- ⏲ 10 min
Pour it over the cold middle layer, spread it thin and leave it only about 10 minutes. While the surface has begun to set but still just marks under a finger, score it into 16 with a knife.
- ⏲ 30 min
Chill at least 30 minutes, ideally two hours. The cocoa butter finishes crystallising.
- ⏲ 5 min
Lift the slab out by the paper and cut along the scored lines. Dipping the knife in hot water and wiping it between cuts keeps the chocolate from cracking. Serve cold.
Tips & Variations
Variations
- Mint or mocha: a few drops of peppermint extract in the middle layer, or strong coffee in place of the milk. Nanaimo has enough versions to support a tourist trail of them.
- Peanut butter: swap half the middle layer's butter for peanut butter, and cut the icing sugar back a little.
- Without custard powder: 2 tbsp cornflour and vanilla. Custard powder is essentially starch with colour and vanilla added.
- Without nuts: coconut and crumbs alone work; the base is just less interesting to chew.
- Thinner: the same quantities in a 23x33cm tin give thinner layers and 32 pieces, which is closer to what most Canadian cafés sell.
Tips
- The top layer shatters because of cocoa butter. Melted chocolate is cocoa solids and sugar suspended in cocoa butter, and that cocoa butter crystallises as it cools. Crystals are hard and they cleave, so a lid of pure chocolate splits the instant a knife touches it and takes a piece of the middle layer with it. The 30g of butter stirred in is structural, not richness — milk fat stays soft at fridge temperature and interrupts the cocoa butter's crystal network. Cooking oils files the two fats in this lid one bullet apart, and chocolate truffles takes the crystals a step further: there is more than one form they can take, and tempering is how you pick one.
- Which is why you score it before it sets. Dobos torte gives the same instruction for a different material and a different reason: that is caramel, and caramel sets as a glass rather than crystals, so it shatters instead. Same movement, different substance.
- The base is set by egg instead of an oven. It is exactly the arrangement cooking eggs prescribes when it says yolk-thickened creams split past 70°C and are therefore made over a water bath. So the bain-marie here is a condition, not a convenience.
- The crumb base itself is not new. Cheesecake and key lime pie already use one. What differs is that this one is not baked — cooked egg and butter are all that hold it.
- Being no-bake is not the interesting part. Tiramisu and panna cotta skip the oven too. What is particular here is that three layers each set cold by a different means.
- The middle layer is not a gel. Icing sugar is mostly undissolved sugar suspended in butter, with around 3% starch in it. So that layer is firm because the butter is firm, and left out at room temperature it simply slumps.
- Warm the knife. Pressed with a dry blade, the chocolate cracks. Dipped in hot water and wiped, it melts its own way through.
The basics behind this dish
- Cooking Oils: Smoke Point and What Each One Is ForWhat a smoke point actually marks, how much headroom deep frying needs, and why sesame oil and extra-virgin olive oil are finishing oils rather than cooking oils.
- Serving Temperature: Why Some Dishes Wait and Some CannotWhy cold dishes need heavier seasoning, why rice and rice cake go stale fastest in the fridge of all places, and the dishes where letting the steam off is the point.
- Eggs: Coagulation Temperatures and What They DecideWhite sets at 62°C, yolk at 68°C. Those two numbers explain scrambled eggs, boiled eggs, steamed custard and crème anglaise all at once.
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