Metasurface optics have offered a fresh perspective into light-matter interactions, providing an unsurpassed means to engineer the wavefront of light transiting a subwavelength interface. However, strictly planar surface architectures using conventional antenna elements have performed quite inefficiently, as they contain purely electric modes and thus do not possess the magnetic modes necessary to generate the optimal Huygens-like scattering profile. And while multi-layer stacks of these 2D sheet admittances have been consistently demonstrated as the only feasible solution to-date for plasmonic-based Huygens-like metastructures, their experimental performance is often degraded by non-analytical behavior or fabrication limitations, leaving dielectric architectures as the best hope for real-world metasurface optical applications. In this work, we propose a new alternative for highly-efficient plasmonic metasurfaces: a 3D architecture which produces a Huygens-like total field and exhibits transmittances of approximately 80% at any targeted phase retardation across the full 2π phase space. The 3D unit cell consists of a cubic silicon cavity, with the interior walls of the cavity modeled as grids of voxels. The grids are initially represented in a binary fashion as a random assortment of either a metal (gold) or a dielectric (air), then iterated through a genetic algorithm routine, flipping the value of individual voxels until a maximum transmittance was reached at the desired total field phase retardation. Optimized designs for eight phase values were chosen to construct a metasurface lens. Simulation, fabrication and experimental results of both the individual element and the lens are presented.