Pointing the recess in the exterior plaster

For our house (timber frame + prefabricated house with WDS), recesses were left in the area of the front doors at the lower part for the installation of the block steps, entrance porches. These have now been installed, but the recesses were quite generous, so there are still gaps on the left and right at the lower part of the front door. How do you fill these in now? The sealing foil and barrier are present.

I was thinking of filling the gaps with mortar/cement and then plastering with the exterior plaster?