Insert the edge of a chisel into the mortar underneath one of the stones in the fascia. You want to insert it close to parallel with the stone itself. If you have trouble getting the edge underneath the stone through the mortar, use a hammer to hit the bottom of the chisel. The force from the hammer helps to break through the mortar under the stone.
Press down on the handle of the chisel to use it as a lever. The stone from the fascia pops off once enough force is applied.
Remove every stone in the fascia using the same process.
Slowly grind the mortar away from the original surface using a disc grinder. Be careful not to grind too deeply or you are going to damage the original surface that was under the fascia.
Wash the mortar dust created by the grinder with water from the surface. Dry it afterwards.