Dunt need butter unless it's just that. Lots and lots of cream so it finishes on yer nose and a great big dollop of jam on top.
Jam first then cream otherwise how on earth do you spread the jam? Edit: don't anyone dare tell me that you just 'drop' jam on top!
Cornish style then. Cornwall is jam spread then cream, Devon is cream spread then jam literally plonked on top
Toasted, with butter and a bit of Frank Cooper's marmalade. Maybe a bit on Wensleydale cheese on the side.