Japanese "Satsuma-imo" Sweet potato muffin version2

My wife likes to bake bread and she also likes Japanese "Satsuma-imo" 薩摩芋 sweet potato so she is always looking for ways to combine the two. She made "sweet potato" rolls using Japanese sweet potato roasted in the Weber grill and then mashed and seasoned with butter and soy sauce. She used the mashed Japanese sweet potato in the bread dough and also as a filling. In this variation she used the recipe for "refrigerator potato bread" but substituted mashed sweet potatoes for the white potato called for in the recipe. The result was this wonderful rolls/muffin. It has a very tender delicate texture and you can definitely taste the mild sweetness of the Japanese sweet potato. This muffin does not have a sweet potato filling because all mashed the sweet potato went into the dough.

Ingredients:
1 pkg. yeast
1/2 cup sugar (plus 1/2 tsp additional to proof the yeast)
1/2 cup warm water
1 cup warm milk
1 1/2 sticks ( 3/4 cup butter softened)
2 tsp. salt
2 eggs
1 cup mashed Japanese "Satsuma-imo" sweet potatoes (make link to my potato recipe) run through a food mill to eliminate any chunks that may remain after the potatoes have been mashed #1.
4 cups bread flour (with more as needed)

Directions:
Day1:
1. Proof the yeast in the warm water and 1/2 tsp. sugar.  Warm the milk with the butter in it. Dissolve the sugar in the milk mixture.
2. Using a mixing paddle on the stand mixer add the warm milk butter mixture, eggs and mashed potatoes blend thoroughly. Add the proofed yeast and salt. Mix completely.
3. Switch to a dough hook and add the flour one cup at a time until the dough clings to the hook and is smooth and springy to the touch. Knead on speed 2 for 7 to 10 minutes.
4. Form into a ball and put into a bowl with a small amount of vegetable oil turning the dough to cover with a coat of the oil. Cover tightly and place in the refrigerator overnight (or as the recipe says up to 16 to 18 hours).

Day2:
1. Next morning punch down the dough. (It will extremely cold and dense so "punch down" may not be the process that is actually possible. Just flatten the best you can) #2. Let rest for about 5 minutes (picture below) #3. Cut off pieces weighing 2 1/4 oz. #4. Form into rolls and place in a heavily greased baking dish several inches apart so they can rise #5. Cover and let rise until doubled. Cook in a 400 degree oven for 18 to 20 minutes until they sound hollow when tapped #6.

These muffins were amazing. The slow rise overnight in the refrigerator resulted in a very fine texture. The flavor was very delicate but clearly tasted of the sweetness of the sweet potato. The combination of the delicate texture and flavor almost felt like we were actually eating fluffy cooked sweet potato rather than bread. So the substitution of sweet potato for regular potato in this recipe worked very well and the end result was equally as good but distinctly different...well worth the variation.