In a stand mixer combine: tangzhong, yeast mixture, melted butter, eggs, vanilla, cocoa powder, food coloring, salt, both flours.
1/4 cup unsalted butter, 2 large eggs, 1 tsp vanilla extract, 1 tbsp red gel food coloring, 2 tbsp unsweetened cocoa powder, 1 1/4 tsp salt, 2 1/2 cups all-purpose flour, 1 cup bread flour