Cauliflower gratin with roasted garlic herb butter

Cauliflower, mozzarella cheese (pasteurized part-skim milk, cheese cultures, salt, enzymes, corn starch [anti-caking agent]), roasted garlic herb butter (grade aa butter, expeller pressed canola oil, garlic [garlic, citric acid], herbs [parsley, basil, oregano, chives], onion salt [salt, dehydrated onion], garlic salt [salt, dehydrated garlic], black pepper), parmesan cheese (pasteurized part skim milk, cheese culture, salt, enzymes [rennet], flow agent: less than 2% microcellulose crystalline to prevent caking), panko bread crumbs (wheat flour, contains 2% or less of the following: sugar, yeast, salt).