In a large mixing bowl, add egg yolks, salted butter, sugar and dessicated coconut. Combine gently with a spatula, then using your hands, knead them until fully incorporated. Refrigerate until ready to use.
Combine bread flour, cake flour, instant yeast, and sugar in a bowl and whisk. If you’re using active dry yeast and have already proofed the yeast in warm milk and sugar, you can just add this to a mixing bowl, together with the remaining quantity of milk and sugar (see Notes at the bottom).
Transfer to an electric stand mixer with dough hook attachment. Add cold milk little by little as you knead on medium speed for 5 minutes. Add oil and continue to knead for another 3 minutes until the dough has pulled away from the sides of the bowl. If the dough is too sticky, add more flour ¼ cup at a time until the dough comes together. By this time, the dough should already come together nicely into sort of a round ball and feel soft and smooth but still slightly tacky to the touch. Do the “windowpane” test (see my Notes below).
Lightly grease a container or large bowl with butter or non-stick cooking spray, and place the kneaded dough in the container. Cover with a clean cloth then refrigerate. Allow the dough to rise overnight in the fridge for 12 hours. It will rise to 1.5x its original size.
Remove the dough from the fridge and let it come to room temperature. Flour a work surface and your hands with a small amount of flour, then lightly punch down the dough and knead it with your hands for 3 minutes into a small oblong roll, making sure to tuck in the sides towards the bottom as you go along. Divide into half, then each half equally into 18 pieces of dough balls (35g each). Add 1 tbsp filling then pinch to seal and shape into ball.
Place the rolls in a lightly greased 9x13-inch pan or on a large, rimmed baking sheet lined with parchment or lightly greased. Space the rolls about 1/2- to 1-inch apart or if you like, 3-4 inches apart (depending on the size of your baking pan) to give them ample room to rise and expand.
Insert a tray filled with hot boiling water at lowest rung of the oven. Cover the rolls with a lightly greased plastic wrap, making sure it's not pinned under the baking sheet or else the rolls will flatten while rising. Let the plastic wrap gently hang over the sides of the pan to fully cover the rolls but not press them down.
Place baking tray inside the oven, close the oven door and allow bread dough to rise for 45 minutes - 1 hour until double or triple in size. Then remove from oven.
Preheat oven to 150 C. Prepare sugar syrup glaze. Bake the rolls for 30 minutes until golden brown. Halfway through (15 minutes), remove tray from oven, brush the crust with sugar syrup, add edible flowers and dessicated coconut then bake for another 15 minutes. Once done, remove from oven, place on a cooling rack and brush the crust again with sugar syrup for a nice shine.