1. Preheat the oven to 170°C and grease and line a 24cm springform cake tin with baking paper

To make the custard:
1. Heat milk and vanilla until hot.
2.Beat the eggs, castor sugar and vanilla then whisk in the cornflour.
3. Slowly add the hot milk while whisking all the time. Return to the saucepan and cook until starting to thicken and starting to boil.
4. Remove from the heat and mix in the butter. Whisk until smooth, scrape into a bowl and cover with clingwrap touching the surface.

To make the cake:
1. Whisk together the oil, castor sugar, egg, vanilla, zest and yoghurt. Sieve together the flour, baking powder and salt and add to the egg mixture.
2. Mix gently together to make the batter. Spoon the batter into the prepared cake tin.
3. Whisk custard until smooth and divide in two. Spoon dollops of one half of the custard around the edges of the cake batter then spread inwards with an offset spatula to smoothen.
4. Scatter over half of the blueberries.
5. Mix the remaining blueberries with the remaining custard and spread onto the cake.
6. Bake for 40 minutes.
7. Cool cake completely on cooling rack in the cake tin.
8. Remove from cake tin and serve at room temp with whipped cream or more FIRST CHOICE Vanilla Dairy Snack.