  In a Mirror Twin World with a maximally symmetric Higgs sector the little
hierarchy of the Standard Model can be significantly mitigated, perhaps
displacing the cutoff scale above the LHC reach. We show that consistency with
observations requires that the Z2 parity exchanging the Standard Model with its
mirror be broken in the Yukawa couplings. A minimal such effective field
theory, with this sole Z2 breaking, can generate the Z2 breaking in the Higgs
sector necessary for the Twin Higgs mechanism. The theory has constrained and
correlated signals in Higgs decays, direct Dark Matter Detection and Dark
Radiation, all within reach of foreseen experiments, over a region of parameter
space where the fine-tuning for the electroweak scale is 10-50%. For dark
matter, both mirror neutrons and a variety of self-interacting mirror atoms are
considered. Neutrino mass signals and the effects of a possible additional Z2
breaking from the vacuum expectation values of B-L breaking fields are also
discussed.
