Place 1/4 cup neutral oil and 1 tablespoon thinly sliced ginger in a small saucepan. Warm gently over the lowest heat for 6–8 minutes — do not let it smoke or simmer— just warm to release aroma. Remove from heat and let steep until cool. Strain out ginger and reserve 1 teaspoon of the infused oil for the tartar. Discard or save remaining oil for other uses.

Tuna Tartar

Prepare tuna and avocado

Pat the sushi-grade tuna dry with paper towels and cut into small, even 1/4" dice. Place diced tuna in a chilled bowl. Dice the avocado into similar-sized pieces and gently reserve in a separate small bowl; toss avocado with 1 teaspoon lime juice to slow browning and set aside.

Make seasoning mixture

In a small bowl combine 1 tablespoon soy sauce, 1 teaspoon toasted sesame oil, 1 teaspoon fresh lime juice, 1 teaspoon ginger oil (from the ginger oil step or pre-made), and the finely minced red chili. Whisk briefly to combine. Taste and adjust: add up to 1/2 teaspoon more soy if you want saltier, or more lime for brightness.

Combine tuna with dressing

Pour about two-thirds of the seasoning mixture over the diced tuna (reserve the remainder to finish). Toss gently with a rubber spatula just until the tuna is evenly coated — do not overmix or mash the tuna. Season with 3/4 teaspoon fine sea salt and 1/8 teaspoon freshly ground black pepper; taste and adjust seasoning as needed.

Fold in scallions and avocado

Gently fold the sliced scallions into the dressed tuna. Then carefully fold the avocado into the mixture, using light strokes to keep the avocado pieces intact. If the avocado softens the mixture too much, refrigerate for 5 minutes to firm slightly before plating.

Finish and plate

Spoon the tuna tartar into a ring mold (2.5–3" diameter) or form quenelle shapes with spoons onto chilled plates. Drizzle the reserved seasoning mixture around or over the tartar (sparingly). Sprinkle toasted sesame seeds and remaining 1/4 teaspoon black pepper over the top. Add microgreens or cilantro as garnish. Finish with a few drops of ginger oil on the tartar for aroma.

Crisp Carrier

If serving store-bought chips

Arrange sturdy potato chips on the serving plate around or beside the tartar. Use chips as scoops for the tartar immediately before serving so they remain crisp.

If making fresh chips

Heat neutral oil in a heavy skillet or deep pot to 350°F (175°C). Thinly slice 1 medium potato (optional) on a mandoline into very thin rounds, rinse and pat dry. Fry potatoes in small batches until golden and crisp, about 2–3 minutes per batch. Transfer to paper towels, sprinkle lightly with salt, and let cool. Serve 2–3 chips per portion alongside the tartar.