In a small bowl, dissolve yeast & 1 tsp sugar in lukewarm milk. Let stand for 5 minutes to allow yeast to activate. In a large bowl, whisk together 2 Tbsp sugar, melted butter, sour cream & egg. Add yeast mixture, stirring to combine.
In another bowl combine flour & salt. Add flour mixture, 1 cup at a time, combining with wet mixture. Once all the flour has been added, knead dough for about 2 minutes until smooth & elastic consistency. Place dough in a greased bowl & cover with plastic wrap & a towel. Allow to rise in a draft free place until doubled in bulk, about an hour.
Punch the risen dough down & divide the dough into 3 equal parts. Lay a piece of parchment paper over the removeable bottom of a 10-inch tart pan on your work surface. Place first portion of the dough on the parchment paper & roll or press out dough the size of the bottom of the tart pan. Carefully spread the circle with half of the bean paste. Roll out the second portion the same size & transfer with your rolling pin to top of the first portion. Carefully spread it with the remaining bean paste.
Roll out the third portion of dough to the same size & place it on top of the other two layers. Pinch the dough around the outer edge to seal. Place a small glass in the center & press down. Cut from outside edge just to the glass, forming 12 wedges.
Remove the glass. Twist each wedge 3-4 times. Tuck edge under. Place bottom of tart pan ( with parchment paper & twists) inside tart pan ring. Cover with plastic wrap & a towel. Allow to rise for about 15-20 minutes.
Preheat oven to 350 F.
Lightly brush twists with a bit of egg wash & sprinkle with black sesame seeds before baking. Bake 25-30 minutes or until golden brown. Remove from pan to a wire cooling rack.
Recipe Notes
When you purchase red bean paste, make sure the ingredients do not include maltose. The type that contains maltose is for making mooncakes. It is quite sticky, and it is hard to work with when making red bean bread.