In a large saucepan, scald milk. Meanwhile, in a bowl, beat eggs until creamy. Add sugars, flour and 1-1/2 cups of the scaled milk; slowly pour into saucepan with remaining milk. Cook and stir over medium heat until pudding thickens, about 15-20 minutes. Remove from the heat; add vanilla and butter. Stir well. Continue to stir pudding every 10 minutes until cooled.