We present a novel heuristic algorithm for two-level Boolean minimization. In contrast to the other approaches, the proposed method firstly finds the coverage of the on-sets and from that it derives the group implicants. No prime implicants of the single functions are being computed; only the necessary implicants needed to cover the on-sets are produced. This reverse approach makes the algorithm extremely fast and minimizes the memory demands. It is most efficient for functions with a large number of output variables, where the other minimization algorithms (e.g. ESPRESSO) are too slow. It is also very efficient for highly unspecified functions, i.e. functions with only few terms defined.