If using sesame crackers, add about an inch of oil to a large, shallow saute pan and set over high heat until it registers 350 F on a candy thermometer. Use tongs to place one sesame cracker sheet in the oil and fry for about 30 seconds; the cracker will puff up. Remove from the oil, place on a plate lined with a paper towel, and let cool. Repeat with the second sheet. Once the sheets are cool, break them into large pieces. Set aside.
To make the tartare, combine the tuna, cucumber, and shallot in a medium bowl and set aside. In a small bowl, combine the sesame oil, soy sauce, Sriracha sauce, and olive oil and stir to combine. Season to taste with salt.
Pour the marinade over the tuna and mix gently. Garnish with the cilantro and serve with the fried sesame rice crackers or shrimp chips.