1tablespoonsugar(12g, dissolved in 1 tablespoon/15 ml hot water)
Start by making the bread dough, and be sure your ingredients are at room temperature. In the bowl of a mixer, add the heavy cream, milk, egg, sugar, cake flour, bread flour, yeast, and salt (in that order). Using the dough hook attachment, turn on the mixer at its lowest setting.
Let it go for 15 minutes, occasionally stopping the mixer to push the dough together. (Note: if you’re in a humid climate, and the dough is too sticky, add more flour ¼ cup at a time until the dough comes together). After 15 minutes, the dough is ready for proofing. Cover the bowl with a damp towel and place in a warm spot for 1 hour. The dough will grow to about 1.5X its original size.
Meanwhile, prepare the filling by thoroughly combining all the filling ingredients in a bowl. Set aside.
After the bread dough has proofed for an hour, put the dough back in the mixer and knead slowly for another 5 minutes to get rid of air bubbles. Dump the dough on a lightly floured surface and cut into 12 equal pieces.
Flatten each piece of dough with your hands into a rough oval shape, about 4 inches long and 3 inches wide. Spread about a tablespoon of filling onto the middle of the dough, and roll it into a cigar, tucking the ends under the bun to completely seal the filling in. We like this method because it evenly distributes the filling throughout the bun.
Transfer the buns to a parchment-lined baking sheet and cover with a clean kitchen towel. Allow to rise for another 45 minutes to an hour.
Preheat your oven to 350 degrees. For the topping, mix together 1/3 cup cake flour, 3 tablespoons softened butter, and 4 ½ teaspoons caster sugar, and transfer to a piping bag or small zip top bag with a small corner cut off. Set aside.
Once the buns have risen, brush with egg wash. Pipe two stripes of your topping mixture onto each bun, and sprinkle each with sesame seeds. Bake for 15-17 minutes until golden. Remove from the oven and brush with the sugar syrup.