Peel and shred carrots. Toss with raisins and salt. Set aside.
In a saucepan mix the flour, sugar, salt and dry mustard. Stir milk in gradually, whisking to mix. Bring to a boil and boil 1 minute. Slowly add 1/4 of the liquid into the eggs while stirring to temper the eggs so they don't cook when added to the hot liquid. Now add the egg yolks in a slow steady stream while stirring liquid. Add the vinegar and butter, boil 1 minute. Let cool and add to the carrot and raisin mixture. Chill before serving.