RHS Plant & Potato Fair recipe - lemon and rosemary drizzle cake

Posted by Joe on

RHS Plant & Potato Fair recipe - lemon and rosemary drizzle cake

A recipe created for the 2015 RHS Plant & Potato Fair. Mashed potato lends moistness and structure to this scrumptious gluten-free lemon and rosemary drizzle cake.

Lemon and Rosemary Drizzle Cake

190g unsalted butter
250g golden caster sugar (plus an additional 115g for the drizzle)
3 lemons, zested and juiced
5 eggs
1 tsp vanilla extract
200g ground almonds
115g polenta (cornmeal)
2.5 tsps baking powder
1 tbsp finely chopped rosemary
2 decently-sized baking potatoes, for mashing – don’t use leftovers!
30g nib sugar (pearl sugar) – you can find this at cake supply stores or online

1. The best way to get your mashed potato, in this instance, is by making use of your microwave. Prick the the potatoes all over with a fork, then zap them until they’re done (around 12-15 minutes on full blast). A skewer should pass all the way through them with no resistance. Cut them in half and leave to cool. Once cooled, push the flesh through a potato ricer or metal sieve, discarding the skins and any tough, uncooked pieces. Reserve 300g for the cake – you can freeze any leftovers and use them for bubble and squeak, or to thicken a soup.

2. Preheat your oven to 180°c (160°c fan). Grease a 9” (23cm) round springform cake tin, and line the base with parchment. Dust the sides of the tin with a little additional polenta to prevent sticking.

3. Weigh together the ground almonds, polenta and baking powder, then whisk to combine.

4. In a separate bowl, beat together the butter and sugar until they’re fluffy and pale yellow.

5. One at a time, add the eggs to the butter-sugar mixture. Beat well after each addition, ensuring that you scrape down the sides of the bowl.

6. Stir in the lemon zest, vanilla extract and rosemary.

7. Fold in the dry ingredients, then stir in small spoonfuls of the mashed potato until it’s all in the bowl and thoroughly combined.

8. Transfer the cake mixture to the prepared tin, smooth the top with a scraper, then scatter over the nib sugar (if using).

9. Bake for 60-70 minutes – when it’s ready, the centre of the cake should offer little resistance when gently pressed with a finger. In the meantime, stir together the lemon juice and additional sugar to make the drizzle.

10. Once the cake is out of the oven, make holes all over the top with a skewer, making sure that they go deep into the cake. Then spoon the drizzle into the holes.

11. Leave the cake to cool in its tin, before turning out and serving.