In a small saucepan over medium heat, scald milk, heavy cream, and vanilla bean by bringing the mixture just to a boil. Remove from heat, cover, and let steep for 10 to 12 minutes. Remove vanilla bean.
In a small bowl, whisk together egg yolks and sugar until light and fluffy, about 2 minutes. Add flour and continue whisking until smooth.
Slowly pour the hot-milk mixture into the egg mixture. Whisk until completely smooth and free of lumps. Return the mixture to the saucepan, and place over medium heat. Bring the mixture to a boil, whisking constantly, and cook for another 2 minutes.
Remove the pastry cream to a bowl. Place a sheet of plastic wrap directly on top of the pastry cream to prevent a skin from forming. Refrigerate until ready to use.