The deterioration of stone monuments generally results in material losses that are traditionally repaired through the use of mortars. The difficulty of this type of intervention on soft stones has resulted in the evolution of restoration techniques toward a new concept: biological mortar. This type of mortar, prepared from stone powder and carbonatogenic bacteria, was derived from the biomineralization stone protection technique. After feasibility tests and in-laboratory optimization, it was possible to carry out a first on-site experimentation following the complete restoration of a French monumental portal. The high-technology approach fits the minimum-intervention principle and adheres to present conservation-restoration ethics in France, increasingly aimed toward a minimal-intervention conservation.