I had shown before that 11.Bd3 is best and gave the line 11.Bd3 Qxd4 12.Nxg6 hxg6 13.Rf1.
But now, oh horror, I see there is a small problem with this as I forgot about 11.Bd3 Qxd4 12.Nxg6 fxg6. It now seems black is equal, maybe even better, as the move I suggested in my book 13.Qg4 (diagram) is not winning.
a/ 13...Bc5 14.Bd2
...a1/ 14...Qf2+ 15.Kd1 16.Nd7 (=+)
...a2/ 14...00 15.Qxe6+ Kh8 16.000 (=)
...a3/ 14...Qe5+ 15.Ne4 (=)
...a4/ 14...Nd7 15.Qxe6+ Kd8 16.000 (=)
b/ 13...Qe5+ 14.Kd1 (=)
c/ 13...Qb4 14.Be3 (+=)
d/ 13...Qd6 14.Ne4 (=)
So the line 11.Bd3 Qxd4 12.Nxg6 fxg6 13.Qg4 seems to be better for black after 13...Bc5 14.Bd2. The problem is that white does not have much alternatives after having played 11.Bd3.
Back to the drawing table !!!