  The standard approaches for describing top quark production and its decay
dynamics are currently mostly either based on the narrow-width (NW) limit or on
off-shell fixed-order calculations. In this article we present a factorised
approach for boosted top quarks that combines the properties of the NW limit
and off-shell computations accounting for the dominant off-shell effects in an
expansion in $m_t/Q$ with the hard scattering scale $Q$. We discuss the key
ideas of our approach and show some preliminary results at tree-level.
