palmer says the traditional way is with home toasted base malt , victory malt or biscuit malt.
i don't have any personal experience but theres a start for you of course all theses malts need mashing with a base malt.
I too like the flavour be it as your description"butty" or as most others "nutty"( LOL)
I think that flavour comes from the malt in that brew and apparently there are three hops that are used as well.
There has been many posts as to the contents and recipes and a search over this forum and Grumpys will give you a lot of ideas.
There has been posts of k & k's, partials, and all grain, recipes but most find it hard to get an exact copy.
I feel it would be a good to finally achieve a clone of that style cause it seems to appeal to to a lot of brewers and it would be a good project for an AG brewer to give it a try.
I would like to give it a go but i need to have my AG working before trying to achieve new recipes.
I've seen the platitude of recipes for this beer but was curious about the particular flavour. I was going to use a Morgans Royal Oak amber ale with 1 or 1.5kg Liquid Amber Ale and was wondering what else I would add.
I seem to remember seeing that recipe and I thought there was some aroma hop or maybe dry hopping as well.
IMO I recon a little bit of Munich malt and maybe some dark crystal in small quantities, but you might not want to do that with the Morgans.
There were many ideas and if you were to give it a go it would be a good idea to make small changes to your base ingredients one at a time and of course keep some notes.
I would ask GMK for his input as I believe he is pretty good with modified kits and extracts and he may be able to help.