Roll the pineapple jam into balls, each weighing 10 g. Cover loosely with clingwrap and let these sit in the chiller while making the pastry dough.
Make the pastry dough:
Sift together cake flour, corn flour, confectioner's sugar, milk powder and salt (omit if using salted butter). Set aside.
Cut the chilled butter into cubes. Place in a large mixing bowl. With your fingertips, rub butter cubes into the flour mixture until the mixture resembles coarse breadcrumbs. While rubbing, keep lifting the flour well up in the bowl. This allows air in between and prevents the butter from softening too much.
Add the yolks, vanilla extract and yellow food colour (optional). Cut into the butter-flour mixture with a fork or flexible scraper. Finish up by hand, mixing lightly until the mixture comes together into a soft and smooth dough.
Roll the dough into balls, each weighing 15 g. If Chill for 10 mins before filling.
Fill and shape the pineapple tarts:
Flatten a ball of dough between your palms.
Place a ball of pineapple jam filling in the centre. Enclose the filling, and gently roll between your palms to smoothen and shape into a golf ball tart.
Place on a baking tray lined with baking paper, spacing the tarts an inch (2-cm) apart.
Place the tray in the chiller for 10 to 15 minutes, before baking. (Note: If you don't have room in your chiller to put in a tray, you can place the tarts close together on a large dish plate, and chill. Once chilled, the tarts will be firm to handle. Transfer to the prepared baking tray, spacing them apart.)
Meanwhile, preheat the oven to 150°C (302°F).
Brush with egg wash and bake:
Brush the tops of the tarts with egg wash.
Bake in the centre of the pre-heated oven for 20 to 25 minutes. Half-way through the baking time, take the tray out of the oven and brush the tarts with a second layer of egg wash.
Bake until the tops are golden brown, and the base of the tarts start to lightly brown, about 25 - 30 minutes. Note: Chilled tarts may take 5 mins longer. As the tarts bake, it is normal for cracks to appear. Do not be alarmed. This is due to the jam expanding outwards as it gets heated. Once the tarts cool, the cracks will shrink.
Let baked tarts cool on the tray for 5 minutes. Then, transfer to a wire rack to cool completely.
How to store pineapple tarts:
Once completely cooled, store in an air-tight container and seal tightly. The tarts will keep well for up to 3 weeks in a cool, dry area. If stored in the chiller, it will keep well for up to 3 months.
How many tarts can the pastry dough make?
Based on a 15 g pastry dough and 12 g pineapple jam filling, this pastry dough can make about 40 large golf ball tarts. For smaller golf ball tarts, I recommend a 10 - 12 g pastry dough and 8 - 10 g jam filling, which makes about 50 tarts.
Is this pastry dough suitable for open-faced pineapple tarts?
This is a tender, melt-in-the-mouth pastry which is not quite suitable for open-faced pineapple tarts as it may be too soft to work with.
Why does the egg wash use oil and condensed milk?
Oil gives the tarts a glossier sheen when baked, while condensed milk renders a deeper brown due to its sugar content. However, you will not even taste the sweetness or flavour of the condensed milk.If you prefer, you can use a simple egg wash made with 2 egg yolks, 1 tsp of water, and a few drops of yellow food colour (optional).