Butterscotch Pudding

I made this butterscotch pudding recipe last night, with mixed results. Taste is delicious; texture not ideal. A little bit lumpy or grainy. Maybe I didn't whisk it enthusiastically enough? I wonder if I would have better results by leaving out the eggs.

I didn't use any whisky and forgot to put in the vanilla extract, but didn't miss these flavorings. Instead of dark brown sugar or cassonade, I used light brown sugar plus a couple spoonfuls of molasses.