In a large mixing bowl, combine lukewarm milk with yeast; whisk until yeast is dissolved. Allow to stand about 3 minutes or until foamy. Add warm mashed potato, melted butter, eggs, sugar, cardamom & salt; mix well. Stir in flour, one cup at a time. When dough is completely blended, turn onto a lightly floured surface. Knead for about 10 minutes, until smooth & elastic.