You have two challot.
R Simcha Bunim Cohen writes in The radiance of Shabbos (p. 77)
Loaves that become attached during baking may be separated and are
still considered whole for the purpose of lechem mishne
In the footnote he refers to Machatzit Hashekel 174:1
Similarly Shmirat Shabbat KeHilchata 55:4:6 writes
Two loaves which became stuck together whilst being baked may be used
as lechem mishneh, even if they are still attached to each other.
However there is a view which disputes this and holds that one must
first separate them.
In the event that one separates them from each other, and they remain
whole, they are indeed considered whole loaves, even if one can tell
they were joined together. Where part of one loaf remains stuck to the
other, it is well to remove the piece, so that the loaf to which it is
stuck should indeed look whole.