Impossible Ube Flan Cake Recipe

The layers of this impossible ube flan cake recipe magically switch places in the oven.

My first time making this kind of cake was when I made a chocoflan cake many years ago. Originally a Mexican creation, chocoflan is a chocolate cake with a thick layer of flan – creme caramel – on top.

It's also known as 'impossible cake' or 'pastel impossible', because of the way the layers magically switch places while baking.

For an authentic chocolate, caramel, followed by cake batter, followed by flan mixture, are layered in that order in a pan and put in the oven. While baking, the dense flan mixture sinks to the bottom while the airier sponge cake rises to the top.

This dessert's Filipino cousin, ube flan cake, is made slightly differently, although the end result is the same.

You still start with a layer of caramel at the bottom of your pan. But instead of layering the cake first, followed by the flan and then the two switching places in the oven, you pour in the flan mixture first. Then, instead of a sponge cake, you make a chiffon cake (flavoured with ube rather than chocolate/cocoa powder), and carefully float the foamy batter on top of the uncooked flan. Then you bake it.

There's a third method that can be used for either type of cake, too: pouring the flan in after the caramel, baking it first, and then pouring the cake batter over the cooked flan before baking a second time.

For all methods, though, you need to bake the cake in a water bath, which makes the heat a bit gentler and helps prevent your flan from scrambling. Making a water bath is simple: you just sit the cake pan in a bigger roasting tin, and then pour hot water into the roasting tin (NOT the cake pan) until it comes up about half the way.

For this recipe, I decided to make an impossible ube flan cake that has the flavours of a Filipino ube flan cake, but the layer-switching magic of a Mexican chocoflan.

Usually, when I make sponge cakes, I swear by butter. But for this particular ube cake, I'm using margarine (specifically Aldi's 'Stork' knock-off, 'Perfect For Cakes'). This is because you need to chill this cake, and cakes with real butter go hard in the fridge. But margarine or oil cakes keep their fluffy softness at any temperature.

I also use mascarpone for the flan layer. Some recipes call for cream cheese, and some call for no cheese at all. I love anything cheesecake-ish, but the cream cheese I used for my original chocoflan caused the flan to split, because there was simply too much water in the cream cheese (a common problem with UK brands).

I knew mascarpone would be a safer bet this time round because the water content is much lower, while the fat content is higher, for a wonderfully smooth, rich flan.

You can also watch me make this on my YouTube channel, Tashcakes:

Ready? Let's go.

Ingredients for Caramel:

200g caster sugar

Ingredients for Flan:

150g mascarpone
1 can condensed milk (397g)][0090
1 can evaporated milk (410g)
4 eggs
1 tsp vanilla bean paste

Ingredients for Ube Cake:

170g margarine (see above why not butter)
170g caster sugar
3 eggs
170g self-raising flour
3 tbsp milk
Pinch of salt
Ube flavouring
Purple food colouring (if your ube flavouring isn't coloured)

Method:

1. Preheat the oven to 180°C and thoroughly grease a bundt pan (with vegetable oil or a little extra softened butter or margarine).

2. To make the caramel, place the sugar in a small saucepan and stir over a medium heat. Keep the sugar moving to make sure it caramelises evenly, and as soon as it's all liquid and golden brown, remove from the heat.

3. Pour the caramel into your tin, give the tin a gentle tilt so the caramel evenly coats the bottom, and set aside.

4. To make the flan layer, simply whisk the ingredients together (be careful not to 'whip it' too vigorously so you don't get too many air bubbles). Set aside.

5. To make the sponge cake, cream the margarine and sugar together until light and fluffy, followed by the eggs. Then whisk in the flour, milk, salt and ube flavouring.

6. Scoop the cake batter into the tin on top of the caramel in an even-ish layer.

7. Gently pour the flan layer through a sieve on top of the cake layer.

8. Cover the top of the tin with foil, and place the tin in a large roasting tray. Fill the roasting tray half-full of boiling water to create a water bath, and bake for one hour.

9. Remove from the oven, take off the foil and leave to cool completely. Pop in the fridge to chill overnight.

10. Unmould the cake carefully, slice and serve.

Enjoy, and have fun.