The stabilization of the continental crust over geologic timescales is reliant upon the stratification of the crust into a felsic upper crust and a more mafic lower crust. This chemical stratification of the crust is deeply influenced by metamorphism and partial melting of the middle-to-lower continental crust. These processes are energy intensive, particularly in the middle crust due to elevated heat fluxes imposed by surface temperatures. Moreover, contrary to the view of a global mafic lower crust, felsic metasedimentary rocks are commonly found in exhumed metamorphic terranes and xenoliths from the deep crust. The presence of these sedimentary rocks, which are typically enriched in heat producing elements (U, Th, K), within the lower crust alters the thermal profile and rheology of the continental crust, potentially leading to destabilization. In this talk I will explore two Variscan middle-to-lower continental crust exposures, the Trois Seigneurs Massif, French Pyrenees, and the Ivrea-Verbano Zone, Italian Alps, to investigate the mechanisms responsible for the addition of sedimentary rocks to the deep crust, alongside the mechanisms and timescales of metamorphism and partial melting of these sedimentary rocks. Massifs formed at the end of the Variscan Orogeny, including these two field sites, record widespread metamorphism and partial melting events within the continental crust, and as such are ideal places to answer long-standing questions regarding crustal formation and evolution.