Place the butter in a small bowl and beat until lightened. Mix in the garlic, basil, lemon zest, salt and pepper. Place a foot long sheet of plastic wrap on a work surface; spoon on the butter. Roll the butter inside the plastic wrap into in a 1” thick log. Place in the fridge until firm, about 1 hour.
Preheat your grill to medium-high. Slice the butter into 1/2” thick rounds and set on a plate. Pat the halibut dry with paper towel, brush with olive oil, and season with salt and pepper. Lightly oil the bars of the grill. Grill the halibut 3 to 4 minutes per side, or until just cooked through. Set the fish on plates, top each with 2 to 3 rounds of the butter, and serve.
Recipe Options: Flavour the butter with a another chopped fresh herb, such as tarragon or dill. Instead of lemon zest, use orange zest to flavour the butter. The butter is great for other grilled fish, such as salmon or tuna steaks. Instead of grilling the halibut steaks, bake them in the oven. To do so, start by preheating the oven to 425 degrees F. Place the halibut in a single layer in a parchment paper-lined baking dish. Drizzle with the olive oil and season with salt and pepper. Bake for 10 minutes, or until cooked through. Top with the butter as described in the recipe and serve.