A method of cross-linking a composition comprising firstly a polyethylene-based silane-grafted polymer, and secondly a filler. The invention is remarkable in that the cross-linking method consists in mixing the composition with a condensation catalyst constituted by lauryl stannoxane of formula [(C.sub.4H.sub.9).sub.2Sn(OOCC.sub.11H.sub.23)].sub.2O.