Scald milk, add butter, sugar, and mashed potatoes. Cool to lukewarm. Mix yeast and warm water in bowl of stand mixer. Let stand 10 minutes. Add milk, butter, sugar, and mashed potato mixture to yeast and water. Stir. Stir in eggs and vanilla. Sift together the flour, baking powder, salt, and add to other ingredients and mix. Add 1/2 cup more flour if needed. Dough should be soft and sticky. Put in greased bowl and turn to coat. Let rise for 1 1/2 hours. Turn out onto floured board and pat to 1/4 inch thickness. You should have a rectangle about 16x22 inches. In medium bowl, mix together brown sugar and 2 1/2 Tblsp. cinnamon. Spread 1/3 cup softened butter on dough. Sprinkle with 1 Tblsp. flour. Sprinkle with brown sugar, cinnamon mixture. You will not need all of it. Sprinkle with raisins and finely chopped nuts. Sprinkle with another tablespoon of flour. Beginning with the long side, with floured hands, roll into a long, tight cylinder. This dough is very soft and may be a little hard to roll. Using a piece of fishing line or sewing thread, slide under the rolled dough and cross at the top and pull gently to cut dough into 1 1/2 inch slices. Place cut pieces in a lightly greased 9x13 inch baking pan. The pan will hold 12 cinnamon rolls. You will need a second pan for the remaining 6 rolls. You can sprinkle some of the remaining brown sugar-cinnamon mixture over the rolls if you want. Put pans in cold oven and turn heat to 350 degrees. Bake for 25-30 minutes or until rolls are golden brown. While the cinnamon rolls are baking, mix together 1/2 cup butter, 1 1/2 cups powdered sugar, 1/4 cup cream cheese, 1/2 teaspoons vanilla, zest from one lemon, juice from 1/2 lemon, and 1 teaspoons half and half in the mixing bowl of a stand mixer. Mix until smooth and creamy. When cinnamon rolls are done, wait about 5 minutes and then frost generously.