Dissolve yeast and sugar in warm water.
Add bread flour, salt, sugar, butter, and the yeast mixture, then knead the dough.
Let the dough rise for the first fermentation.
Divide the dough, shape it into balls, and apply the tiger pattern topping.
Shape into bagels and let it rise for the second fermentation.
Blanch the bagels in boiling water.
Bake in a preheated oven.