Mash butter into the brown sugar with a spatula or the back of a spoon, until there are no more lumps of butter and the mixture has form a paste. (Note: The butter will need to be soft for this to work.) Combine and sift flour and corn starch, then stir into the butter mixture until combined. Wrap the mixture with plastic wrap, pat the mixture down to form a disk and refrigerate until firm (about 1 hour). Roll dough between 2 sheets of baking paper to 2mm thick. Use a 4cm round cutter to cut 12 discs and an 8cm cutter to cut another 12. If the mixture is too soft to cut, place dough onto baking tray and refrigerate until firm. Once all the discs have been cut, chill until ready to use.

Bring the water, butter, sugar and salt to a boil in a medium saucepan. Remove the pan from the heat and quickly stir in the flour with a wooden spoon.

Cook the mixture over medium-high heat, stirring constantly with the wooden spoon, until the mixture pulls away from the sides of the pan and film forms on the bottom of the pan, around 1-2 minutes.

Transfer the dough to a large mixing bowl allow to cool (about 2 min). add one egg and using either a hand mixer or wooden spoon mix it in until well combined. Add additional eggs one at a time repeating process. You’ll know the batter is ready when you can put it between two fingers, and it doesn’t break apart when you pull them apart. Please note: You may additional eggs, you may need less than four eggs. The important thing is to look for the right consistency in the batter.

Preheat the oven to 220C (425F) and prepare two baking sheets with parchment paper. Fit the end of a piping bag with a round tip and pipe x12, 2 cm rounds and x12 3cm (slightly taller) rounds, spacing them about 3 cm apart to allow them to puff as they bake. Place chilled cookies on top and bake for 20 min. turn the oven off and allow them to cool in the oven.

To fill with pastry cream, use the end of a teaspoon to create a hole at the bottom of each puff and fill with pastry cream using a piping bag.

In a large mixing bowl, mix the yolks, vanilla bean paste and the sugar and whisk until well combined and the mixture lightens in colour. Add the corn flour and plain flour and stir until mixture is smooth, add baileys and milk and stir well. Then slowly add the rest of the milk while stirring.

Transfer to a medium sized saucepan and stir on medium heat until mixture thickens and becomes smooth. You should be able to run your finger along the back of the spoon and it will be thick enough to not come back together.

Add the cold butter cubes and stir until well combined.

Transfer custard to a bowl, cover with plastic wrap and refrigerate for at least 3-4 hours or overnight to allow it to completely set.

Preheat a fan-forced oven to 160C (320F) or 180C (356F) for a conventional oven. Line a cupcake tin with cupcake liners.

In the bowl of a stand mixer fitted with the paddle attachment, add the flour, baking powder, caster sugar and salt. Turn mixer on low speed and allow it to mix for a couple minutes to help everything combine well (alternatively you may do this by sifting the ingredients together). Add the softened butter and let it mix until it resembles a fine sand like texture.

Next, add milk, eggs, yogurt, oil and vanilla bean paste in a large jug and whisk well.

Add wet ingredients to dry ingredients in a slow and steady stream until no dry ingredients are visible. Scrape down the bowl and mix for another 20 seconds.

Fill each cupcake liner 3/4 of the way (using an ice cream scoop to transfer the batter into the cupcake liners makes this a quick and easy process otherwise you can use two tablespoons).

Bake for 20-25 min or until a toothpick inserted comes out clean. Allow them to cool completely on a wire cooling rack before frosting.

To assemble cupcakes, core the centre and fill with custard. Stick large puff on top, then add a dollop of custard on top of that puff and stick second puff on top.