How to Make It
In a bowl, combine the corn oil and ginger and let stand at room temperature for at least 2 hours. Strain the oil.
With a very sharp knife, cut the tuna into 1/8-inch dice. In a large bowl, combine the tuna with 3 tablespoons of the ginger oil, 3 tablespoons of the cilantro and the jalapeño, wasabi, sesame seeds, scallion and lemon juice. Mix gently and season with salt and pepper.
Stand a 1 1/2-inch-tall and 2 1/4-inch-round mold or a biscuit cutter in the center of a salad plate. Fill the mold with tuna tartare, pressing gently. Lift off the mold. Repeat with the remaining tartare.
Drizzle the remaining ginger oil around each tartare and sprinkle with the tomato, the remaining tablespoon of cilantro and a squeeze of lemon juice. Stand 5 potato chips in a circular pattern in each tartare and serve immediately.