Granular consistency in homemade butterscotch pudding is a common, tricky challenge. It happens when the egg yolks curdle when they are added too quickly to the hot milk mixture. Graininess can be avoided by: (a) carefully and deliberately tempering the egg yolks before adding them to the hot milk mixture. (b) whisking constantly as the eggs yolks are being added to the hot milk mixture. You can usually fix grainy pudding by straining the mixture through a fine-mesh sieve.