I came across some videos about how to cook mackerel (Chef Saito's Saikyo-zuke with Spanish Mackerel [Japanese Cooking] - Dining with the Chef) and several of them recommended the use of a "fish cooking sheet" that looks to me just like aluminum foil.  They put this foil on top of a frying pan and then put the fish on top of the foil and then cover with a glass lid on low heat for 3-4 minutes before flipping. Note, the fish is not sealed inside the foil with herbs and spices, and the recommendation is for low heat. If any, what is the culinary purpose of using foil for frying pan (when cooking oily fish)? It says one side is non-stick, but surely it is not just for help with clean up?  Does it modify the heat in some special way not otherwise achievable without the use of foil? The foil is from Japan, but the pictures on the packaging make it clear what it's used for. [Bulk Purchase] Kitinto-san Foil Sheet for Frying Pans, Wide 11.8 x 2.6 ft (30 x 7 m) x 4 Packs    
It's a silicone-coated aluminum foil. It's just something that makes your life easier when cleaning. You could just use a regular non-stick pan to get the same benefits. There's no "culinary purpose" for it. 