Question is as interesting as the animal jackalope.
We ASSUME that incomplete dominance of the number of horns gives rise to 0,1 or 2 horns, where hh=>0, Hh=>1 ("blend" of 0 and 2), and HH=>2 horns.
So if HH crosses with hh, the genotype of the offspring will be Hh, i.e. phenotype Hh=> 1 horn