Bursting Blueberry Crumb Cake

Bursting Blueberry Crumb Cake! Think – blueberry crumble meets warm lemon cake with a crunchy buttery streusel topping and melty scoop of vanilla ice cream. It tastes even better than it sounds! 

Bursting Blueberry Crumb Cake

I’ve done my fair share of blueberry desserts but I’ve always wanted to do a cake with an outrageous amount of blueberries in it. As in, BURSTING with blueberries. Not just studded. I dreamed of a blueberry crumble, except in cake form. (Yes, these are the thoughts that occupy my mind at night).

The question really was just how much blueberries I could bake into a cake without weighing down the sponge so much it became dense.

I peaked out at 500g (1lb). That’s almost double the typical amount used in most Blueberry Crumb Cakes.

And with extra blueberries comes extra streusel, that crumbly crunchy caramel top. I guess sometimes dreams can come true!!

Ingredients in Bursting Blueberry Crumb Cake

Here’s what you need to make this.

The blueberries

The blueberries are tossed in a little flour and sugar so it forms a jam-like layer that mostly suspends on the surface of the cake. The lemon is used to provide wetness to make some of the flour stick to the blueberries.

You will find that not all the flour sticks to the blueberries. Be sure to scatter it all across the blueberry layer. We need the full 3 tablespoons of flour to ensure the blueberries don’t sink. Initial versions of the cake only used 1 tablespoon and the blueberries dispersed a little too much for my liking.

Frozen blueberries will work too! Use frozen because they bleed a lot when thawed.

The Crumb Topping

This is called a streusel in baking. It’s a mixture made with flour, sugar and butter combined to make a lumpy mixture that is used to add a terrific crunchy topping on the surface of cakes, muffins, bars etc.

No unusual players here. The only one worth noting is sugar. I prefer using caster sugar (superfine sugar) because the grains are finer so I can be confident that I won’t end up with sugar grains in the streusel. However, if you don’t have it, just substitute with regular sugar.

Lemon Cake

The Lemon Cake is adapted from the batter I use for my classic blueberry yogurt cake. However, the batter is a little sturdier built to withstand the combined 700g / 1.4lb of blueberries and streusel that we pile on top and still come out lovely and springy at the end.

PS I know that 700g/1.4 lb sounds like an insane amount of blueberries and streusel, but we do lose weight in liquid evaporation as it bakes.

• Flour – just plain / all purpose flour. It’s best to use plain flour and add baking powder rather than self raising flour. Cakes just never rise as well.

• Baking powder – This is what makes the cake rise. If yours is old, it’s best to check it’s still active! 

• Sour cream – This helps make the sponge lovely and moist because it adds wetness into the batter but it’s thicker than milk. So we can use less flour for the same volume of batter. Ensure the sour cream is at room temperature, ie not fridge cold, else it will not incorporate properly into the batter (eg it can make the melted butter solidfy. Yup, been there, done that!).

• Milk – Full fat is best though low fat will work fine too. As with the sour cream, ensure it’s not fridge cold. Take it out 30 minutes prior, or microwave for 10 seconds.

• Eggs –  Use large eggs which are ~55 – 60g / 2 oz each (they come in cartons labelled “large eggs”) at room temperature. See here for what this means, and a quick way to de-chill fridge cold eggs!

• Melted butter – Once melted, let it cool for a bit. It can still be warm, we just don’t want it to be super hot.

• Lemon zest – Zest the lemon before you squeeze out juice to coat the blueberries! It’s impossible to properly zest a lemon once it’s been squeeze of juice. We only use the zest because it adds lovely lemon flavour. The juice, on the other hand, mainly just adds sourness.

• Vanilla extract – Better flavour than imitation vanilla essence. I personally don’t use vanilla bean or vanilla bean paste in cakes because I think it’s wasted. Save it for things like Crème Brûlée and Flan Pâtissier!

• Salt – Just a touch, to bring out the other flavours in the cake. Standard baking practice these days.

How to make Blueberry Crumb Cake

Streusel first (it’s a quick mix), then toss the blueberries, then make the batter last.

1. How to make Streusel

1. Mix the dry ingredients (flour, sugar, cinnamon and salt). Then add the melted butter and vanilla, and mix using a fork just until all the flour is wet but the mixture is still clumpy.

2. This is what you’re after. Lots and lots of lumps!

2. zest lemon fiRst, then toss the blueberries

1. Zest the lemon then keep it for the batter. Do this before juicing the lemon for the blueberries because it’s impossible to zest a lemon that’s been squeezed of juice!

2. Toss the blueberries in lemon juice first to wet the surface. Then toss with the flour and sugar. Then set aside until required.

3. The lemon cake batter

1. Line a 20cm / 8” springform cake pan with baking / parchment paper. See here for my easy way of doing it – no pencil required!

   It needs to be a springform pan so the cake can be removed without inverting (which would cause the crumbly topping to fall off!)

2. Whisk dry – Whisk the dry ingredient in a bowl (flour, baking powder and salt).

3. Whisk wet – Then in a larger bowl, give the sugar, vanilla, zest and eggs a good whisk for about 15 seconds until the surface is a bit foamy. Add the melted warm-not-hot butter and sour cream, then whisk until smooth. 

4. Add flour in 3 batches – Add one third of the flour then use a rubber spatula to fold it through. Once mostly incorporated, add half the remaining flour, fold through, then the remaining flour and fold through.

5. Milk last – When you can no longer see flour, add the milk and mix until incorporated. If you see tiny bits in the batter, it will be the zest not flour lumps! 

6. Batter thickness – This is what your batter should look like. Pourable but not super thin like my Chocolate Cake and not super thick like a muffin batter.

4. ASSEMBLING AND BAKING

1. Pour the batter into the cake pan and smooth the surface.

2. Top with blueberries. For the most even spread, start from the outer edge then work your way in. If you start in the middle, the weight of the blueberries pushes the batter out and up the walls of the pan. But, don’t get too hung up on this step! This is a rustic cake, and the blueberry layer is always a bit of a pot-luck situation in terms of spottiness / jammy patches / how neat the line is (it is not, ever!).

3. Use residual flour – Make sure you tip the residual flour and sugar at the bottom of the blueberry bowl over the blueberries. We need all the flour to ensure the blueberries don’t sink (I had problems when I used slightly less flour). 

4. Streusel – Then cover the top with the streusel, using your fingers to make nice big lumps across the surface. Aim for around 85% coverage – it’s nice to have some jammy blueberries peeking through the golden brown crumbly topping!

   TIP: If you have powdery streusel at the bottom of the bowl, just clench a pile of it in your fist to make it clump together. Then break up into clumps and scatter! 

5. Bake for 65 minutes at 200°C/400°F (180°C fan-forced), rotating halfway to ensure the streusel browns evenly. 

   Note on oven temperature: it’s a little higher than the usual temperature for baking cakes because the blueberries and streusel add a thick protection layer so we need an extra blast of heat to cook the cake through. At the typical 180°C/350°F (160°C fan), the cake was taking 75 – 80 minutes and the sponge rose a smidge less.

6. Cool for 10 minutes in the pan to give it a chance to stabilise. Then unclip the sides and use a spatula to slide the cake onto a cooling rack. Cool for a further 10 minutes before slicing to serve warm (so the ice cream melts!), or fully cool and serve at room temperature.

Warm vs room temperature serving

If you want to be a normal, this cake can be served at room temperature, with optional ice cream or whipped cream on the side. That’s the normal way Crumb Cakes are served. It is delicious and the way this cake was originally intended to be.

But, for the ultimate Blueberry Crumb Cake experience, serve it warm with a scoop of melty vanilla ice cream on top. It is just such a comforting combination – the warm blueberries that burst in your mouth mingling with the cool creamy ice cream, the crunchy bits of caramel-y streusel topping and the soft cake (which gets softer when warm!) with the hint of fresh lemon flavour.

I am firmly planted on the warm-serving side. Try it once, and I think you will be too! – Nagi x

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Watch how to make it

Life of Dozer

Me: in Brisbane, at the final Good Food & Wine Show for the year. Dozer: at the Golden Retriever Boarders’ house. She’s always a little offended because Dozer gives her husband a more enthusiastic greeting than she gets. 

She is a vegetarian. Her husband is a carnivore. Dozer is not subtle.

This is a photo she sent me yesterday of Dozer waiting at the gate to greet her husband when got home from work!