The chemical composition of a young embedded protostar may trace the physics that take place during star and planet formation. As recent studies allude to planet formation taking place during the early stages of star formation, we need to constrain the physical and chemical structure of young disks. One of the major questions in astrochemistry is whether or not the disk inherits the chemical inventory of the natal cloud. To shed light on this question, we used the Atacama Large Millimeter/submillimeter Array to spatially resolve a young embedded Keplerian disk around the Class I protostar TMC1A. Rotational transitions of simple molecules are mapped at a spatial resolution of a few au. The inferred molecular abundances of these species are then compared to its surrounding envelope, Class II protoplanetary disks, and Solar System Objects. We have shown that the molecular composition of the surface layer of this young disk is inherited from its envelope. The similarity of its chemical structure to the more evolved protostellar systems indicate that a significant fraction of the molecular inventory of planet-forming disks is set during the early stages of disk formation.