Put all ingredients in a medium bowl and mix until well combined. Lay out a sheet of plastic wrap and form the butter into a log on top of it. Close wrap, twist ends and refrigerate until use. Can be frozen for up to 3 months. Add a layer of foil around the plastic wrap before freezing.

Preheat grill on high or oven to 400°. Slice off the top of each head of garlic, exposing cloves.

Place garlic on a sheet of foil, drizzle with oil and close foil to form a packet. Roast about 30 minutes, or until soft (if using grill, put foil package on the side, away from direct flame). When somewhat cooled, squeeze garlic out of cloves and mash with a fork.

Preheat grill on high or oven to 400°.

Trim fish fillets as needed to fit cedar planks. Place each one skin side down on a plank and top with scallion butter slices or chunks, to taste. Season with kosher salt and a light dusting of ground pink peppercorns. (Note: Pink peppercorns are very pungent, so use sparingly.)

Place the planked whitefish directly onto the hot grill and close the lid. Grill-roast for 8–10 minutes (depending on the size of your fillets and temperature of your grill) or until flesh flakes easily with a fork. (Note: It’s helpful to have a spray bottle with clean water to extinguish any flare-ups on the edges of the planks.)

If using an oven, place the planked whitefish onto a wire roasting rack placed on a sheet pan. This will allow air circulation, and the sheet pan will catch any butter drippings. Roast 8–10 minutes or until flesh flakes easily with a fork.

Serve on the cedar plank. Add grilled lemon wedges for presentation.