  We propose a novel way to formulate Chiral Perturbation Theory in a nuclear
background, characterized by a static, non-uniform distribution of the baryon
number that describes the finite nucleus. In the limiting case of a uniform
distribution, the theory reduces to the well-known zero-temperature in-medium
ChPT. The proposed approach is used to calculate the self-energy of the charged
pion in the background of the heavy nucleus at O(p^5) in the chiral expansion,
and to derive the leading terms of the pion-nucleus optical potential.
