You will need this https://www.thriftbooks.com/w/the-official-guinness-cookbook/27154772/?resultid=689a5437-8f3c-455f-bce0-4cda140ba81e#edition=58161133&idiq=46015173 Happy cooking!
I saw that book on Amazon, and was surprised that it didn’t seem to have a Welsh Rarebit recipe.
But here’s one:
https://thehappyfoodie.co.uk/recipes/welsh-rarebit/