Add your blueberries into a food processor and process until smooth. Push this through a sieve.

Pour this into a pot and add the sugar, then mix. Place this onto medium heat and heat, just until the mixture starts to simmer.

Mix together the corn flour and water, then pour this into the pot. Keep heating whiles stirring, until the mixture thickens.

Leave this to cool in your fridge for 30 minutes.

In a pot, add the lemon juice, water and sugar. Mix all this together.

Place onto medium heat and heat until the mixture comes to a boil.

Take it off the heat and leave this aside to cool down at room temperature.

Once the blueberry puree has cooled down for 30 minutes, we can make the mascarpone cream.

Add your mascarpone into a bowl and beat this for about a minute, we are just doing this to loosen it up. Leave this aside.

Add your double cream into a separate large bowl and whip this, just until you get soft peaks. Leave this aside too.

In a pot, add some water and place this onto medium heat. Let this come to a simmer.

Now in another large bowl, add the egg yolks, the sugar and the salt. Whisk these together, then place this bowl on top of your pot. Make sure that the simmering water isn't touching the bottom of the bowl. If it is, pour some of the water out.

Keep whisking for about 3 minutes. The mixture should lighten in colour and the sugar will have dissolved after 3 minutes. During this process, make sure that the water underneath is simmering, NOT BOILING. If it is, lower the heat. We don't want the egg yolks to get too hot.

Take this bowl off the heat, then add the mascarpone into this, as well as the vanilla and the cooled blueberry puree. Mix until combined.

Add a large dollop of the whipped cream into this and whisk this in.

Now add half of the remaining whipped cream and fold this in. Then add the rest of the whipped cream and fold this in too.

Get a sponge finger and dip this into the lemon syrup, just dip it for about 2 seconds on each side.

Place this into a 9 inch square cake tin or dish. Then keep repeating this until you have a layer of dipped sponge fingers in your tin.

Add half of the mascarpone cream on top of the sponge fingers, spread this out.

Add another layer of dipped sponge fingers, then add the rest of the mascarpone cream.

At this point, I dusted some freeze dried blueberry powder on top, but this part is optional.

Leave this to set in your fridge overnight.

The next day, cut into it and enjoy!