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We propose to observe with XMM-Newton (120 ks) and HST (2 orbits) the luminous quasar HE 0238-1904 (z=0.63) comma which is host to one of the best studied UV outflows to date. The inferred mass outflow rate and kinetic luminosity are typical of AGN where intense feedback is at work. HE 0238-1904 was detected in the XMM-Newton Slew Survey comma but no X-ray spectrum of this exceptional object has ever been acquired with any major X-ray observatory. Our aim is to obtain for the first time high-quality X-ray data of HE 0238-1904 comma in order to understand the physical properties of its innermost regions comma in terms of obscuration comma intrinsic spectral shape comma and possible presence of an X-ray counterpart to the UV wind. This observation will allow us to shed new light on the link between efficient accretion comma powerful winds comma and AGN feedback.