Cut and core the pineapple until you’re left with just the flesh, then cut it into chunks and blend it in a blender or food processor for 20-30 seconds. It doesn’t have to be liquid smooth, some small chunks are fine. Pour this pineapple slushy into a medium pot or saucepan, and add in the sugar, molasses, salt, vanilla extract, cinnamon, star anise, and cloves. Place over medium heat and simmer, stirring occasionally, until the jam is reduced in volume by two-thirds, turns amber in colour, and no liquid remains, about 45 minutes. (Take care not to scorch the bottom of the pot, especially as the jam thickens towards the end of cooking.) Turn off the heat, remove and discard the whole spices, then set the jam aside to cool to room temperature.
Tangzhong starter
Whisk together the water, whole milk, and bread flour in a small saucepan. Cook this over medium heat for 3-5 minutes, until thick. Then, transfer this into the bowl of a stand mixer (or a big bowl if you’re mixing by hand).
Dough
In the same bowl, add in the milk, egg yolks, butter, yeast, bread flour, granulated sugar, and salt. Knead this on a stand mixer with a dough hook attachment on low speed for 12-15 minutes, until a smooth dough forms. (You should be able to do the window test with the dough.) If the dough is too wet or too chalky, feel free to add more flour or water accordingly.
First proof
When the dough is done, shape it into a large ball and let it proof in a large bowl, covered, for 60-90 minutes, until the dough has doubled in size.
Shaping and second proof
When the dough has proofed, punch it down, then divide it into 55g balls. You should be able to make 12 balls this way. Roll each dough piece into round balls, then place them onto a lined baking tray (you might need two, actually), leaving at least a 5cm gap in between each bun. Let the buns proof again, covered, for 45-60 minutes, until they’re about 50% larger.
Bun topper
For the bun topper, just mix all the ingredients for it together in a bowl, and knead it until smooth. Split it into two roughly equal portions,, shape each one into a palm-sized disc, and let them chill for at least 15 minutes in the fridge.
Preheat oven
Heat an oven to 180°C (356°F).
Assembly
When the buns are nearly fully proofed, take one piece of the bun topper dough out of the fridge. Using a rolling pin, roll it out in between two sheets of parchment paper until about 3mm thick. (I rolled it into an oval about 30cm long and 20cm wide.) Then, using a 8cm ring cutter, cut out circles in the dough, and immediately transfer each circle on top of each bun, gently pressing it and easing it down so the top of the buns are neatly covered. Repeat for the other piece of bun topper dough. (If the dough circles are too soft to transfer, you can chill the rolled out dough in the fridge for 1 minute, parchment and all, then try again.)
Scoring
Using a paring knife, score a shallow criss-cross pattern on the bun topper, then brush the bun with the egg wash (this is just made with the 2 egg yolks beaten together).
Baking
Bake the buns in the oven for 18 minutes, until the tops are brown and craggly. When done, take the buns out of the oven and let them cool for at least 5 minutes before consuming.
Eating
The polo buns are great as is, but for an extra luxurious experience, slice the polo buns horizontally in half (or tear them if you wish), and spread a generous amount of pineapple jam onto the bottom half of the bun. Put the top bun on top, and eat your pineapple-y polo bun sandwich!