Make the tangzhong by mixing flour and milk in a nonstick pan over medium heat until a thick paste forms.
Mix tangzhong with cold milk, yeast, and sugar. Rest for 10 min to activate the yeast.
Add all other ingredients except half of the butter. Knead for 5 minutes at medium speed. Add the remaining butter and knead for 5-7 more minutes until a smooth dough forms.
Cover and let it rise for 60-90 min in a warm place until it doubles in size.
Roll out into a 1 cm thick circle. Cut out the donuts (~3.5” diameter) and holes. Gather dough scraps into a ball and roll out again until the dough is used up.
Place donuts in a tray and let them rest for 30 minutes.
Heat 2 inches of oil in a wok. Once it reaches 350F, turn the heat to medium-low and fry donuts 3 at a time for about 45-60 seconds per side. Fry the holes for about 90 seconds.
Make the original glaze by mixing all ingredients.
For the chocolate glaze, melt the chocolate and mix in the oil.
Mix the sugar and cinnamon.
While still warm, dip your donuts one by one into the glazes, and roll the donut holes in the cinnamon sugar.