  The availability of simultaneous X-ray and Very High Energy (VHE)
observations of blazars helps to identify the plausible radiative contributors
to the VHE emission. Under leptonic scenario, the VHE emission from BL Lacs are
attributed to the synchrotron self Compton (SSC) emission. However, many BL
Lacerate (BL Lacs) have shown significant hardening at VHE after correction for
the Extra Galactic Background Light (EBL) attenuation. We study the spectral
hardening of two nearby BL Lac objects, Mkn 421 and Mkn 501 having most number
of simultaneous X-ray and VHE observations available among all the blazars.
These BL Lacs are relatively close and the effect of EBL attenuation is
relatively minimal/negligible. We study the scatter plot between the X-ray
spectral indices and intrinsic VHE indices to identify the plausible origin of
the VHE emission. For Mkn 501, the VHE spectral indices are steeper than X-ray
spectra, suggesting the scattering process happening at extreme Klein-Nishina
regime. On the other hand, for Mkn 421, the VHE spectra is remarkably harder
than the X-ray spectra, which suggests an additional emission mechanism other
than the SSC process. We show this hard VHE spectrum of Mkn 421 can be
explained by considering the inverse Compton (IC) emission from a broken power
law electron distribution with Maxwellian pileup. The possibility of the
hadronic contribution at VHE {\gamma}-rays is also explored by modeling the
hard spectrum under photomeson process.
