Easy Sourdough Vanilla Sheet Pan Cake with Caramel Buttercream

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Easy Sourdough Vanilla Sheet Pan Cake whips up in minutes and bakes into the most beautifully textured cake! Soft, light and buttery, this sheet pan cake is the crowd-feeding, palate-pleasing dessert of your dreams! Adapted from my Sourdough Vanilla cake, this luscious cake is dairy free and egg free, and can even be sugar free, too!

Why You’ll Love This Recipe

• A great Sourdough Discard Recipe – if you are feeding your starter and looking for a recipe to use up your discard, this is a great one! It uses a good cup of starter, so you’ll be able to give your pet a good feeding!
• Quick and Easy – there’s no need to ferment this cake batter if you don’t have time. No creaming of butter or whipping of eggs required. This is a straightforward recipe that slaps together in minutes!
• Cheap to make – there are no weird or expensive ingredients in this cake, so it’s extra gratifying that it’s such a success with guests.

Ingredients

For the Cake

• Flour – use all purpose flour for the best results. can be substituted 1:1 for oat flour.
• Sugar – I use castor sugar. For a sugar free version, use Truvia (using about a third of the amount that you would sugar).
• Baking powder and baking soda – leavens this cake. You need both for the best cake texture!
• Salt – cake is gross without salt, believe me! You’d be surprised the difference this makes.
• Sourdough starter – use discard or fed starter, it makes no difference since the sourdough does not actually leaven the cake. Note, you can ferment the cake batter to reduce the phytates in the flour, just be sure to add the baking powder and soda just before baking.
• Water (or whey or milk if you can tolerate it) – I use whey, since I strain my homemade yoghurt and this gives me a lot of whey to use up.
• Neutral oil (I use Rice Bran oil) – you could also use vegetable oil or canola oil. Let me know if you try it with any other oil! for sweet cakes, its best to use oil with a subtle flavour.
• White vinegar – activates the baking soda and powder.
• Vanilla essence – use a LOT to really get a good vanilla flavour. I used about 2 tablespoons, but you could definitely use more! Note that vanilla extract has a better flavour, so if you have that on hand you definitely won’t need to use as much!

Caramel Buttercream

• Vegan or dairy butter – I used dairy butter, but this buttercream could definitely be made with a vegan spread if you have a dairy intolerance. Just make sure it is a spread that is solid at room temperature!
• Golden syrup – golden syrup is the magic ingredient that turns this frosting into delicious caramel decadence.
• Dash of Milk – stops the buttercream setting too brittle in the fridge.
• White chocolate chips – helps to set the frosting when cooled, and also provides that sweetness!

Method

Sourdough vanilla sheet pan cake is a really easy, zero effort cake to mix and bake.

Line a large 18″x 11″ baking dish with baking paper, and preheat the oven to 160 Celsius. This cake bakes low and slow so that it cooks evenly.

In a large bowl, sift together the flour, sugar, baking powder, baking soda, and salt. Sifting the dry ingredients really does make a difference to the final texture of the cake. You will be glad you went to the extra effort! This step also mixes the dry ingredients together – two birds, one stone!

In a separate bowl, measure and mix together the starter, oil, water, vinegar and vanilla essence.

Carefully pour the liquid mixture into the dry ingredients and fold together into a smooth batter. Mixing the dry ingredients and the liquid ingredients in separate bowls prevents over-mixing and contributes to a better textured cake.

Pour into the prepared sheet pan, and bung into the preheated oven. Bake for 35 minutes or until a skewer inserted into the middle comes out clean.

Caramel Buttercream

This Caramel Buttercream is s easy to make – no need to cream butter and sugar or worry about curdled eggs. Use a dairy free spread for the buttercream to make this wonderful dessert completely vegan.

Melt the butter and golden syrup over a medium heat. Boil for 4 minutes. Add a dash of milk (about 1/4 – 1/3 cup) and stir. Adding a dash of milk to the icing will ensure the caramel buttercream does not set rock hard. It’ll still be firm, but not brittle.

Remove from the heat and add the white chocolate chips.

Refrigerate this mixture for 30 minutes. It’ll look a bit runny when you remove it from the fridge, but just you wait! The idea is for the mixture to cool and firm up a wee bit so that when you whip it, it stabilizes and gets to that classic fluffy buttercream texture.

After 30 minutes, whip up the caramel mixture with an electric whisk. It’ll thicken, get lighter in colour, and expand a lot! Spread over cooled cake. This buttercream will firm up in the refrigerator for a luscious, fudge-like topping.

This sourdough vanilla sheet pan cake needs no adornment, garnishes or sides. It is perfect on it’s own, which makes it the best and easiest party food!

Top Tips for The Perfect Cake

To make the best sheet pan vanilla cake, follow these tips:

1. Use Room Temperature Ingredients: Ensure eggs, butter, and milk are at room temperature for a smooth, well-blended batter and a fluffy cake. Take them out of the fridge 30-60 minutes before baking.
2. Sift the flour: Sifting flour really does make a difference to the final texture of the cake. You will not regret taking this extra step!
3. Mix the liquid and dry ingredients separately: I’m all for one-bowl baking, but mixing the dry and liquid ingredients separately really does prevent over-mixing and ensures the cake is light and airy.
4. Prepare the Pan: Grease thoroughly and line with parchment paper for easy removal. Use butter or non-stick spray and leave parchment overhang for easy lifting.
5. Monitor Baking Time: Sheet pan cakes bake quickly. Check for doneness a few minutes before the recommended time. A toothpick inserted in the center should come out clean or with a few moist crumbs.