1. When buying fish to be used for sushi, ideally order the fish skinned, with all grey color from the bottom removed. I used a full side of salmon here, alternatively, you can opt for four-to-eight-inch-long portioned fillets. We will use this to create a “brick” of fish to use for sashimi, nigiri, raw fish platters, sushi salads and regular rolls. Always look for salmon with thick, even white lines of fat. Salmon with plenty of well distributed fat is more flavorful, like a well marbleized steak (although the fat on salmon is a lot more healthful). If you’re not buying a full side of salmon, make sure not to buy the tail of the fish, which isn’t thick enough to form a nice brick and won’t taste as good for sushi.
2. This next step is very important and will make a huge difference in the taste and texture of your fish (this applies to meats as well). With all fish, raw or cooked, it’s best to remove as much moisture as possible. This will make the fish firmer, easier to handle and more palatable. To remove moisture, wrap it in paper towels one or two at a time, until the paper towel comes off clean. While still wrapped in paper towel, let it chill in the fridge. It will be firmer and easier to slice evenly when very cold. The drying process is best done after the fish is already prepared as bricks because more surface area means more wet flesh is exposed, and we want to remove as much moisture as possible.
3. To create your salmon brick, first cut off the tail. Then cut lengthwise from the beginning of where the salmon slopes downwards. The same goes for the fatter side. Where the salmon dips downward, slice that off lengthwise as well. Use the trimmings for spicy salmon or for poke bowls, although it will be more difficult to get nice-looking slices. Now you should have a large rectangle. Next, slice lengthwise down the middle then widthwise down the middle. Now you should have four even brick-like pieces. (See 2nd picture in the gallery.)
4. Fresh tuna will often be sold as single steaks, with a somewhat triangular shape. We are looking to get rectangular slices, so cut off the top of the triangle, leaving you with a rectangular shape (see 3rd picture in the gallery). Use the scraps for spicy tuna and other dishes such as the Lemon Mint Tuna below.