(1) Middlegame Kingside Lever

What is White's best move?

1.h5 This is a Kingside Lever that can pressure Black into playing g5 and weakening the critical pawn structure of the kingside light squares.

If 1...gxh5 2.g3 planning Kg2 with the idea of Rh1, or Nh4.

Now if 2...Bg4 3.Kg2

followed by Rh1, Nxg4 and Nh4 etc.