In a small saucepan, combine shortening and milk. Heat until shortening is melted; set aside to cool. Dissolve the yeast and 1 teaspoon sugar in the warm water.
In a large bowl, beat the eggs, 1/2 cup sugar, and salt together. Add the milk mixture and yeast mixture to the egg mixture, stirring to blend. Sift in the flour and baking powder, and mix well. Cover, and refrigerate overnight.
Divide dough into fourths, and roll out on a floured surface. Spread surface with the soft butter. Cut dough into triangles, and roll up from larger to small end.
Place rolls on a baking sheet, and allow to rise for 3 to 4 hours. Preheat oven to 400 degrees F (200 degrees C.)Bake rolls for 8 to 10 minutes in the preheated oven, or until golden brown.