  The extreme electromagnetic fields sustained by plasma-based accelerators
allow for energy gain rates above 100 GeV/m but are also an inherent source of
correlated energy spread. This severely limits the usability of these devices.
Here we propose a novel compact concept which compensates the induced energy
correlation by combining plasma accelerating stages with a magnetic chicane.
Particle-in-cell and tracking simulations of a particular 1.5 m-long setup with
two plasma stages show that 5.5 GeV bunches with a final relative energy spread
of $1.2\times10^{-3}$ (total) and $5.5\times10^{-4}$ (slice) could be achieved
while preserving sub-micron emittance. This at least one order of magnitude
below current state-of-the-art and paves the way towards applications such as
Free-Electron Lasers.
