Cut the tuna into a fine dice, about 1/4"-1/2" cubes. Place tuna cube into a large bowl, and combine with shallots and soy sauce. Stir to mix.
Mix in the lime juice, sriracha, sesame oil, and ground ginger. Add a pinch of salt to taste, and add additional salt to fit your taste preferences if necessary. Set bowl aside.
In a medium bowl, add the peeled avocado, lime juice, and garlic powder. Mash with a fork until relatively smooth and spreadable. Add a pinch of salt, stir to combine, and taste. Add more of anything if you prefer.
In a smaller bowl, whisk the mayonnaise, sriracha, and the juice from a lime wedge together. Taste, and add a pinch of salt, or more of the other ingredients if you prefer.
Place a large biscuit cutter directly onto a plate. Spoon the tuna mixture into the biscuit cutter to fill it halfway, then top with mashed avocado until the biscuit cutter is full. Gently remove the biscuit cutter, lifting directly upwards. Lightly set the biscuit cutter on top of this tuna avocado stack, and repeat to make a four layer stack of tuna / avocado / tuna / avocado. Repeat on other plates to create additional four layered stacks.
Spoon the spicy lime drizzle into a small, plastic zip-top bag. Snip a small corner off of one end, and gently push the sauce towards the corner. Squeeze the sauce through the corner, zigzagging over the top of the tuna and avocado stacks, to create a clean line pattern for the garnish. Sprinkle sesame seeds over the tops of each stack.
Serve with crispy wontons, or eat by the spoonful!