Based on the shadow wave function we have developed the first microscopic theory of the interface between a quantum liquid and solid. We overcome the difficulties present in other variational theories because no a priori equilibrium positions for the atoms have to be assumed and localization of particles is exclusively due to interparticle correlations. We find that the crystalline order parameters vary smoothly over the interface and the interface itself is mobile. We have extended the previous wort (Phys. Rev. Lett. 72, 2589 (1994)) to the {111} interface of a fee crystal of He-4. The interfacial energy is 0.16 K/Angstrom(2), the width of the interface is about 15 Angstrom and the local density has a dip on the liquid side.