Mix the tangzhong ingredients together. Cook over low heat, stirring constantly, until thick and sticky. Let cool, then refrigerate for 4-6 hours or overnight. Before making the bread, let it sit at room temperature for 1 hour.

Combine all the dry ingredients in a bowl.

Mix the milk and sweetened condensed milk together. Warm in the microwave for about 30 seconds until just warm, then stir to combine. Pour into the bowl with the dry ingredients and mix well. Knead by hand for about 5 minutes.

Add the softened unsalted butter and knead for another 5-10 minutes until the dough is smooth and no longer sticky. Cover with plastic wrap and let rise for 1 hour.

After 1 hour, punch down the dough to release air. Divide into 3 equal pieces, shape each piece, and place in a loaf pan. Let rise for another 1 hour.