On the stove or in microwave, heat Milk (3/4 cup) so that it is warm (about 100 degrees F/37 degrees C), but not hot. In a large bowl, mix in Instant Dry Yeast (1 3/4 teaspoon) and set aside ten minutes, until mixture is frothy. Mix in Caster Sugar (1 tablespoon), Salt (1/4 teaspoon), Ground Cinnamon (1 teaspoon), Unsalted Butter (2 tablespoon), Sweet Potato (1/2 cup), and Egg (2).
In separate bowl, whisk together Whole Wheat Flour (1/2 cup) and All-Purpose Flour (2 1/2 cup) then slowly incorporate flour into the potato mixture. When mixture forms a loose ball, throw it onto a floured surface and knead for a few minutes, adding a touch more flour as needed, until you have a smooth dough ball. Rinse out your large bowl, grease it, and set dough back into the bowl. Cover bowl with plastic wrap or a warm wet towel and set somewhere warm. Allow dough to double in size.