X-core is a novel foam core material developed by Donkervoort Automobielen, it enables a unique one-shot process for seamless composite sandwich structures with mould-defined features all-around. The foam is co-cured to carbon fibre/epoxy prepregs, in this form the process is currently used to make car components for the Donkervoort D8 GTO RS. One of the main challenges that is faced in the manufacture of these ‘bare carbon’ components is the visible presence of surface defects. In this research a variety of process variables are primarily correlated to the surface porosity content of the laminate. Processing guidelines pertaining to the cure cycle, core material composition, moulding and type of prepreg are formulated based on these relations. The main causes for surface porosity are identified and it is found that the process is especially sensitive to the laminate composition: Variations in stacking sequence and fibre aerial weight.