4cupsall purpose flour, fluffed and levelled(500g)
2 1/2cupspowdered icing sugar
In a large bowl with an electric mixer, beat butter and sugar on high until creamy.
Add eggs, vanilla, and sour cream and beat until smooth.
Add baking soda, baking powder and flour and beat on low until combined -- dough will be soft, almost like cake batter. THIS IS FINE.
Preheat oven to 350 degrees F and line baking sheets with parchment paper. Drop by heaping tablespoonfuls onto baking sheets 2-3 inches apart and bake for 10-12 minutes, until edges are golden and centers are set.
FrostingWith an electric mixer, beat butter until smooth. Add sugar, vanilla and milk and beat until smooth, adding additional sugar or milk to reach desired consistency (you don't want it too thin!).