Mix bread flour, cake flour, sugar, salt, and instant dry yeast.
Add milk, whipping cream, whole egg, and condensed milk. Knead by hand for about 10 minutes (stand mixer recommended).
Add unsalted butter at room temperature and knead until smooth. Place in a bowl and cover with plastic wrap.
Let rise in a warm place for about 1 hour, or until doubled in size.
In a separate bowl, mix egg yolks, sugar, and vanilla bean paste.
Add cornstarch and mix. Add warm milk and mix well. Heat over low heat.
Once bubbles start to form, remove from heat, add unsalted butter, mix well, strain, cover with plastic wrap, and cool.
Punch down the risen dough to remove gas. Divide into 5 portions, shape into balls, cover with plastic wrap, and let rest for 15 minutes.
Flatten one dough ball, remove gas, fill with custard, and seal to form a round shape.
Place in a mold, cover with plastic wrap, and let rise for about 40 minutes, or until doubled in size.
For the cookie topping: Cream unsalted butter, mix in sugar, then mix in cake flour, and finally add milk and mix.
Brush the risen bread with milk and pipe the cookie topping diagonally.
Bake in a 180°C oven for 18-20 minutes (preheat oven to 200°C).
