
This luxurious appetizer, inspired by the renowned Masa, brings the exquisite flavors of high-quality tuna and a briny 'ocean jewel' pop to your home kitchen.
Ensure your sushi-grade tuna is very cold. Pat it dry thoroughly with a paper towel. Using a very sharp knife, carefully cut the tuna into small, uniform 1/4-inch (approx. 0.6 cm) dice. Aim for clean cuts to avoid mashing the fish. Place the diced tuna in a medium bowl.
In a small bowl, whisk together the low-sodium soy sauce, toasted sesame oil, finely grated ginger, mirin (if using), and granulated sugar (if using). Stir until the sugar is dissolved.
Pour the prepared sauce over the diced tuna. Gently fold the sauce into the tuna mixture using a spoon or spatula. Mix just until combined, being careful not to overmix, which can bruise the delicate fish.
To plate, place a 2-3 inch (approx. 5-7.5 cm) round ring mold in the center of each chilled serving plate (or on a single large platter if serving family style). Spoon the tuna mixture into the mold, gently pressing it down to form an even layer. Carefully lift the mold.
Generously top each tuna tartare portion with the tobiko or ikura. The roe provides the crucial briny pop and visual appeal that replicates the 'caviar' essence.
Sprinkle the finely minced chives over the top of each tartare for a fresh, aromatic garnish.
Serve immediately with thinly sliced cucumber rounds, nori crisps, or plain unsalted crackers on the side for scooping.