  We describe a way to continue the fermionic renormalization group flow into
phases with broken global symmetry. The method does not require a
Hubbard-Stratonovich decoupling of the interaction. Instead an infinitesimally
small symmetry-breaking component is inserted in the initial action, as an
initial condition for the flow of the selfenergy. Its flow is driven by the
interaction and at low scales it saturates at a nonzero value if there is a
tendency for spontaneous symmetry breaking in the corresponding channel. For
the reduced BCS model we show how a small initial gap amplitude flows to the
value given by the exact solution of the model. We also discuss the emergence
of the Goldstone boson in this approach.
