Heat the milk in a medium-sized heavy based pan and add the scraped-out seeds from the pod and the pod. Bring to a simmer then take off the heat and cover and allow to steep for a min of 30 minutes (or longer).

Fill a large bowl with ice and water to make an ice bath for the custard.

In a bowl stir the sugar, cornstarch (salt if you are using unsalted butter). Add the egg yolks and whisk until pale and fluffy (I used a hand-held electric beater).

Remove the cover and vanilla pod from the milk, and slowly add it to the egg mixture while whisking continuously. Once it is well mixed add it back into the same pot and put it back onto a medium heat and cook for about 5 minutes until the pastry starts to thicken. Keep whisking continuously. Once it starts to bubble, set a timer and cook for a further 1 minute (this step is important in thickening the custard.)

Remove it from the heat, add the butter and whisk until it's incorporated and glossy. Push the custard through a fine sieve into a bowl and place this bowl into the ice bath. Immediately cover the custard with a piece of baking paper or cling film. This will prevent a skin from forming.

Refrigerate until you are ready to use. Whisk it up before using it to fill these profiteroles.

Preheat your oven to 200C/400F.

Heat the water and milk in a medium-sized pot and add the butter. Bring it to a boil and then remove from the heat and immediately add the flour. Beat until well combined and cook this for a further 2 minutes stirring continuously. The dough should read 75 - 80C/165-175F on a digital thermometer and be pulling away from the sides of the pan. Allow to cool for a few minutes.

Add the pastry to e bowl of a stand mixer fitted with a paddle attachment and beat until there is no more steam coming off.

Once it has cooled to around 63C/145F you are ready to add the eggs. Add them one at a time beating until they are well combined before adding the next one. They might look a little split at first but the batter will come together. Another way to tell if the pastry cream is ready is when you pull the paddle up, the pastry makes a V shape off the bottom. It should be thick enough to pipe.

Fill a piping bag with a 2cm round nozzle and fill it with the pastry cream.

Line a large baking sheet with baking paper and lightly brush the paper with water or spritz with a water from a spray bottle. Pipe around 18 mounds of pastry allowing space between them.

Dip your finger in water and press down on any sharper tips that may have formed.

Bake for 10 minutes at 200C then turn the oven down and bake for a further 20 minutes. Do not open the oven during this time.

To create crispier profiteroles, turn the oven off and wedge  the door so that it is ajar and allow them to cool in the oven  

Place the icing sugar and cherry preserve in a bowl and mix to combine. Use a fork to smooth out any pieces of cherry in the jam if desired.

Fit a small, pointed nozzle on the end of a piping bag, and fill this with the whisked pastry cream. Make an incising at the bottom of each cooled profiterole and pipe a dollop into the cavity.

Add a small dollop of cherry icing glaze to the top of each profiterole and arrange on a circle on a flat round plate. Place about half the cherries in the middle. Arrange the second tier of filled and iced profiteroles between the ones arranged on the bottom layer. Pile more cherries into the middle and dust them with icing sugar.

Decorate with sprigs of rosemary that have been dusted with icing sugar.