As you can see from the photo our mantel casts a very large and annoying shadow when the primary ceiling light is off. The one can light is slightly of center. I'm looking for way to better light the fireplace section of the wall without having the room brightly lit.
Your lighting is single source from above. Casts a single cone of light and the deep shadow you don't want. A couple of options ...
1. Remove the recessed light and replace with two new lights situated on both sides of the fireplace. Pull the lights away from the fireplace wall to get better coverage. This will provide overlapping cones and reduce shadow lines. Use an eyeball trim piece to direct the light sideways along the wall.
2. Reposition the canister light to the center of the fireplace and pull it back from the wall to get better coverage. Since you are doing some drywall work anyway, install a 4' LED strip light on the underside of the mantel. Switches are dimmable so the strip can provide soft or bright light as you choose.