It's a slice of dark rye bread with butter and chieves.
Rye bread is more common in Middle Europe than white wheat bread ... it's tastier... and healthier... and more substantial.
Oh yes, the one downside to our holiday in England was the bread. Toast is fine for breakfast, but how a nation can survive without any "real" bread will stay a mystery to me. Just kidding. But when you come from Germany it really is a bit bizarre to discover that there isn't even something remotely similar to what you are used to be the standard in any supermarket or bakery.
That said - that could be butter on that slice of bread, but here in Germany it could also be "Quark". A dairy product that seems almost equally rare in Britain and the US as dark rye bread. (At least I did gather that much when trying to find the correct translation at Leo.org.) But it tastes even better with chives than butter does. I really adore the chives bread, and I hope I can manage to breed me one soon. (And I'll definitely have a few in my evening meal.)