Custard would go well with many of the other dessert recipes in grandma’s notebook :).
No. 3 below says add ‘flavouring’ with no further indication as to what this refers to. My guess is that it would probably be vanilla essence or flavouring. In case you don’t already know, supermarkets often sell imitation vanilla flavouring as well as genuine vanilla essence (which is noticeably more expensive), so do be aware of what you are getting.