  Functional Renormalisation Group (FRG) equations are constructed for a simple
Yukawa-model with discrete chiral symmetry, including also the effect of a
nonzero composite fermion background beyond the conventional scalar condensate.
The evolution of the effective potential of the model, generically depending on
two invariants, is explored with help of power series expansions. Systematic
investigation of the effect of a class of irrelevant operators on the lower
(stability) bound allows a non-perturbative extension of the maximal cut-off
value consistent with any given mass of the scalar field.
