  Using on-shell amplitude methods, we derive a rotating black hole solution in
a generic theory of Einstein gravity with additional terms cubic in the Riemann
tensor. We give an explicit expression for the metric in Einsteinian Cubic
Gravity (ECG) and low energy effective string theory, which correctly
reproduces the previously discovered solutions in the zero angular-momentum
limit. We show that at first order in the coupling, the classical potential can
be written to all orders in spin as a differential operator acting on the
non-rotating potential, and we comment on the relation to the Janis-Newman
algorithm. Furthermore, we derive the classical impulse and scattering angle
for such a black hole and comment on the phenomenological interest of such
quantities.
