Preheat oven to 425˚F.

Blend together roasted garlic, mayonnaise, and Parmesan.

Heat the butter in an oven-proof pan over low heat.

Sprinkle both sides of the fish with salt and pepper.

When the butter is melted, add the halibut and put it into the oven for 10 minutes. The fish should be just cooked and opaque throughout.

When the halibut is done, pull it out and generously smear the mayonnaise mixture on the top.

Switch the oven to a high broil and return the pan to the still-hot oven for 4 minutes under the broiler, until the top is almost entirely golden brown.

Remove and serve immediately.