Step 1: Rinse the salmon steaks under cold running water, then blot them dry with paper towels. Brush olive oil on one side of each steak. Place one salmon steak, oiled-side down, at a diagonal on each cedar plank.

Step 2: Set up the grill for indirect grilling and preheat to medium-high.

Step 3: When ready to cook, spread the glaze mixture evenly over the top and sides of the salmon steaks. Place the salmon steaks on their planks in the center of the hot grate, away from the heat, and cover the grill. Cook the salmon until cooked through and the glaze is golden, 20 to 30 minutes. To test for doneness, insert an instant-read meat thermometer through the side of a salmon steak: The internal temperature should be about 135 degrees F. Another test is to insert a slender metal skewer in the side of the fillet for 20 seconds: It should come out very hot to the touch. Transfer the planks and the salmon steaks to heatproof plates. Garnish each with a shiso leaf, if desired.