Purple Yam Two-Tone Bread - cooking recipe

Ingredients

Tangzhong Starter
50 g bread flour (1.75 ounces)
250 ml water (1 cup)
Ubi Dough
100 g bread flour (3 1/2 ounces)
25 g powdered purple yams (7/8 ounce)
18 g sugar (1 tablespoon 1/2 teaspoon)
1 g salt (1/2 teaspoon)
2 g instant dry yeast (1/2 teaspoon)
40 g starter tangzhong water roux
40 g warm milk (just under 1/4 cup)
12 g eggs (1/2 ounce 1 tablespoon)
15 g butter (1 tablespoon 1/2 ounce)
Light Dough
125 g bread flour (almost 1 cup or 4 3/8 ounces)
18 g sugar (5/8 ounce)
1 g salt (1/2 teaspoon)
2 g instant dry yeast (1/2 teaspoon)
40 g starter tangzhong water roux
40 g warm milk (just under 1/4 cup)
12 g eggs (1/2 ounce 1 tablespoon)
15 g butter (1 tablespoon)

Preparation

Starter:
In a bowl, whisk together the water and the flour until the mixture is well blended and lump free. Stir the mixture while it cooks over the medium heat to reach 65C/149\u00b0F It takes about 3-5 minutes. It will have a glue like texture.
The key to this starter is the temperature of the water and flour is mixed together than cooked. At a 65 C/149 F temperature, the gluten within the flour absorbs all the water and become leavened. When this mixture is cooled and added to the remainder of the dough, the moisture is retained in the dough and heighten.
Prepare the ubi dough by placing all the ingredients except butter in a mixing bowl. Mix with dough hook at slow speed for 1 minute. Switch the speed to medium and continue mixing until a dough forms. Add butter gradually and mix for approximately 5 minutes on medium speed until gluten is fully developed, i. e. elastic, smooth, non-sticky and leave from sides of mixing bowl. Prepare the light dough at the same way.
Place the two doughs in two lightly greased plastic bags separately and let rise for about 45 minutes at the warm area. Once they are doubled in bulk, punch down and allow the doughs, covered, to rest on a lightly floured work surface for 10 minutes.
Roll out each dough to a rectangle, about 22x10cm. Place purple taro dough atop the light and roll up tightly, beginning at short side. Place in a greased 26cm loaf pan. Cover and let rise till double in bulk, 45 to 60 minutes. Bake at 170C/340F for 30-35 minutes or until done. Remove from pan and let cool on a wire rack.