How to Make It
In a saucepan over medium-low heat with a deep fry thermometer inserted, bring oil to 250°. In a large mixing bowl, combine shallots and flour to lightly coat shallots. Shake off excess flour. Add shallots to the oil and fry until golden brown, about 4-5 minutes. Transfer to a paper towel-lined plate and season lightly with salt to taste.
Reheat oil to 325°. One at a time, fry tortillas until lightly golden brown, about 2 minutes on each side. Transfer to a paper towel-lined plate and season lightly with salt.
In a mixing bowl, combine avocado, lemon juice and salt. Mash with a whisk, leaving small chunks. Set aside.
In a mixing bowl, combine all slaw ingredients. Mix until ingredients are evenly distributed and set aside.
In a small mixing bowl, combine all the vinaigrette ingredients. Whisk until fully incorporated
Add 1/2 cup fish sauce vinaigrette to the slaw and mix until fully incorporated. Let stand for 2 minutes to marinate. Start building the tostadas by spreading 1 tablespoon of avocado mash on each tortilla. Thinly layer hamachi slices on top of avocado mash and season with kosher salt. Add a pile of slaw to each tostada and top with shallots.