  We describe a new microscopic approach for analyzing interacting electron
systems with local moments or, in principle, any local order parameter. We
specialize attention to the doped Mott insulator phase of the Hubbard model,
where standard weak-coupling perturbation methods fail. A rotationally
invariant Stratonovich-Hubbard field is introduced to decouple the static spin
components of the interaction at each site. Charge degrees of freedom are then
treated by ``slave'' Hartree-Fock in the presence of a spatially varying random
spin field. The effective action reduces to a classical Heisenberg model at
half filling, insuring that the system has (i) finite-range order at T>0 with
an exponentially diverging correlation length and (ii) a one-electron
Mott-Hubbard gap in the presence of disorder. Away from half-filling properties
are determined by strongly non-Gaussian fluctuations in the amplitude and
orientation of the local spin fields. The saddle point equations of the theory
at zero temperature reduce to inhomogeneous Hartree-Fock, so that disordering
of domain walls at finite temperature is in principle included. We present
preliminary small system results for the intermediate and large interaction
regimes obtained by Monte Carlo simulation of random spin field configurations.
