I wish I had a chessboard available. It's hard for me just to look at these :D

And if black's last move was g7-g5, then white wins with h5-g6 en passant.

But if black's move wasn't? It's an incomplete problem. What if g5 got there in a two moves?

Ou! I just noticed something! If castling is possible, neither King not Rook may have moved. So the only piece that moved for black is the pawn. But it took me some moments to realize, that the pawn could not have come from g6, but HAS to have come from g7.

I won't say why yet. Look at the board and turn it back one move. Then you will see.

You got the solution!

I'm impressed. It took me an hour or so.

Liberals win again!

Great puzzle! :-D

It's complete. Think why it's not possible for the pawn to get there in 2 moves.
Best ever. And I'm not saying this lightly. I've been solving chess puzzles since times immemorial.

Ah, because the king wouldn't be on f5 you mean? The setup still might have occurred at some earlier point.
What if the king just moved to f5 after g5? But then it would be blacks turn. Yepp you're right afterall.

No. If the pawn was on g6, the king either was in check (and would have had to move away) or he moved into check, which is illegal. So black's last move can't have been g6-g5 because the pawn can't have been on g6.

Yea, I figured later and edited my answer.

I've lost the book, but it looks like one of the problems I saw in Vladimir Nabokov's poem anthology, which he ended with a couple dozen chess puzzles like that. I'll try to find it and see if my memory is correct, but even if I am wrong, since you said you like those sorts of puzzles, you should check it out.
EDIT: Oops. InkPanthers link included the source, sorry. Still, might be worth it to check out the book. It's called Poems And Problems.

Sounds good. I like chess problems and I like poetry. I'll check it out.
... or maybe not.
https://www.amazon.de/Poems-and-problems/dp/0070457247/ref=sr_1_1?ie=UTF8&qid=1528727821&sr=8-1&keywords=poems+and+problems

SPOILER
Mm.. this didn't seem that difficult, I think:
- white king to E6
- black king to F8 (if black moves the tower, loses anyway)
- white tower to D8
- check mate
SPOILER END

I try these puzzles once in a while, but I'm often not sure (maybe not in this example):
- what are the black&white players' sides and so what's the allowed direction for pawns.
- who is moving first? If it says "White mates in 2" it always means that it's his turn, right?
- if special rules like the castling are still possible (e.g: is the king still in the its original place?)


SPOILER2
Ah lol, castling was possible here.
Would the king end up in G8 and the tower in F8?
SPOILER END

Yep. That's the straightforward answer. The tricky part was to figure out what to do if castling is still allowed for black. Because then Ke6 doesn't work:

white: Ke6
black: castles
--> checkmate in 2 averted.