  We show how to detect optimal Berry--Esseen bounds in the normal
approximation of functionals of Gaussian fields. Our techniques are based on a
combination of Malliavin calculus, Stein's method and the method of moments and
cumulants, and provide de facto local (one-term) Edgeworth expansions. The
findings of the present paper represent a further refinement of the main
results proven in Nourdin and Peccati [Probab. Theory Related Fields 145 (2009)
75--118]. Among several examples, we discuss three crucial applications: (i) to
Toeplitz quadratic functionals of continuous-time stationary processes
(extending results by Ginovyan [Probab. Theory Related Fields 100 (1994)
395--406] and Ginovyan and Sahakyan [Probab. Theory Related Fields 138 (2007)
551--579]); (ii) to ``exploding'' quadratic functionals of a Brownian sheet;
and (iii) to a continuous-time version of the Breuer--Major CLT for functionals
of a fractional Brownian motion.
